Storing data in a dispersed storage network

ABSTRACT

A method begins by a processing module of a dispersed storage network (DSN) sending a set of write commands to storage units of the DSN regarding storage of a set of current revision level encoded data slices and receiving a write acknowledgement in response to a write command. The method continues with the processing module determining whether a write threshold number of write acknowledgements have been received. When the write threshold number of write acknowledgements have been received, the method continues with the processing module issuing a set of commit commands to the storage units. The method continues with the processing module determining whether to issue a set of finalize commands, where a finalize command instructs a storage unit regarding storage of a corresponding current revision level encoded data slice and storage of a previous revision level encoded data.

CROSS REFERENCE TO RELATED PATENTS

The present U.S. Utility Patent Application claims priority pursuant to35 U.S.C. §120 as a continuation-in-part of U.S. Utility applicationSer. No. 13/080,431, entitled “READ OPERATION DISPERSED STORAGE NETWORKFRAME”, filed Apr. 5, 2011, issued as U.S. Pat. No. 9,047,242 on Jun. 2,2015, which claims priority pursuant to 35 U.S.C. §119(e) to U.S.Provisional Application No. 61/328,000, entitled, “DISPERSED STORAGESYSTEM ACCESS PROTOCOL FORMAT AND METHOD,” filed Apr. 26, 2010, all ofwhich are incorporated herein by reference in their entirety and madepart of the present U.S. Utility Patent Application for all purposes.

U.S. Utility patent application Ser. No. 13/080,431 also claims prioritypursuant to 35 U.S.C. §120 as a continuation of U.S. Utility applicationSer. No. 13/073,948, entitled, “DISPERSED STORAGE NETWORK FRAME PROTOCOLHEADER,” filed Mar. 28, 2011, issued as U.S. Pat. No. 8,625,635 on Jan.7, 2014, which claims priority pursuant to 35 U.S.C. §119(e) to U.S.Provisional Application No. 61/328,000, entitled, “DISPERSED STORAGESYSTEM ACCESS PROTOCOL FORMAT AND METHOD,” filed Apr. 26, 2010, all ofwhich are incorporated herein by reference in their entirety and madepart of the present U.S. Utility Patent Application for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable

BACKGROUND OF THE INVENTION

Technical Field of the Invention

This invention relates generally to computing systems and moreparticularly to data storage solutions within such computing systems.

Description of Related Art

Computers are known to communicate, process, and store data. Suchcomputers range from wireless smart phones to data centers that supportmillions of web searches, stock trades, or on-line purchases every day.In general, a computing system generates data and/or manipulates datafrom one form into another. For instance, an image sensor of thecomputing system generates raw picture data and, using an imagecompression program (e.g., JPEG, MPEG, etc.), the computing systemmanipulates the raw picture data into a standardized compressed image.

With continued advances in processing speed and communication speed,computers are capable of processing real time multimedia data forapplications ranging from simple voice communications to streaming highdefinition video. As such, general-purpose information appliances arereplacing purpose-built communications devices (e.g., a telephone). Forexample, smart phones can support telephony communications but they arealso capable of text messaging and accessing the internet to performfunctions including email, web browsing, remote applications access, andmedia communications (e.g., telephony voice, image transfer, musicfiles, video files, real time video streaming. etc.).

Each type of computer is constructed and operates in accordance with oneor more communication, processing, and storage standards. As a result ofstandardization and with advances in technology, more and moreinformation content is being converted into digital formats. Forexample, more digital cameras are now being sold than film cameras, thusproducing more digital pictures. As another example, web-basedprogramming is becoming an alternative to over the air televisionbroadcasts and/or cable broadcasts. As further examples, papers, books,video entertainment, home video, etc., are now being stored digitally,which increases the demand on the storage function of computers.

A typical computer storage system includes one or more memory devicesaligned with the needs of the various operational aspects of thecomputer's processing and communication functions. Generally, theimmediacy of access dictates what type of memory device is used. Forexample, random access memory (RAM) memory can be accessed in any randomorder with a constant response time, thus it is typically used for cachememory and main memory. By contrast, memory device technologies thatrequire physical movement such as magnetic disks, tapes, and opticaldiscs, have a variable response time as the physical movement can takelonger than the data transfer, thus they are typically used forsecondary memory (e.g., hard drive, backup memory, etc.).

A computer's storage system will be compliant with one or more computerstorage standards that include, but are not limited to, network filesystem (NFS), flash file system (FFS), disk file system (DFS), smallcomputer system interface (SCSI), internet small computer systeminterface (iSCSI), file transfer protocol (FTP), and web-baseddistributed authoring and versioning (WebDAV). These standards specifythe data storage format (e.g., files, data objects, data blocks,directories, etc.) and interfacing between the computer's processingfunction and its storage system, which is a primary function of thecomputer's memory controller.

Despite the standardization of the computer and its storage system,memory devices fail; especially commercial grade memory devices thatutilize technologies incorporating physical movement (e.g., a discdrive). For example, it is fairly common for a disc drive to routinelysuffer from bit level corruption and to completely fail after threeyears of use. One solution is to utilize a higher-grade disc drive,which adds significant cost to a computer.

Another solution is to utilize multiple levels of redundant disc drivesto replicate the data into two or more copies. One such redundant driveapproach is called redundant array of independent discs (RAID). In aRAID device, a RAID controller adds parity data to the original databefore storing it across the array. The parity data is calculated fromthe original data such that the failure of a disc will not result in theloss of the original data. For example, RAID 5 uses three discs toprotect data from the failure of a single disc. The parity data, andassociated redundancy overhead data, reduces the storage capacity ofthree independent discs by one third (e.g., n−1=capacity). RAID 6 canrecover from a loss of two discs and requires a minimum of four discswith a storage capacity of n−2.

While RAID addresses the memory device failure issue, it is not withoutits own failure issues that affect its effectiveness, efficiency andsecurity. For instance, as more discs are added to the array, theprobability of a disc failure increases, which increases the demand formaintenance. For example, when a disc fails, it needs to be manuallyreplaced before another disc fails and the data stored in the RAIDdevice is lost. To reduce the risk of data loss, data on a RAID deviceis typically copied on to one or more other RAID devices. While thisaddresses the loss of data issue, it raises a security issue sincemultiple copies of data are available, which increases the chances ofunauthorized access. Further, as the amount of data being stored grows,the overhead of RAID devices becomes a non-trivial efficiency issue.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a computingsystem in accordance with the present invention;

FIG. 2 is a schematic block diagram of an embodiment of a computing corein accordance with the present invention;

FIG. 3 is a schematic block diagram of an embodiment of a distributedstorage processing module in accordance with the present invention;

FIG. 4 is a schematic block diagram of an embodiment of a grid module inaccordance with the present invention;

FIG. 5 is a diagram of an example embodiment of error coded data slicecreation in accordance with the present invention;

FIG. 6A is a schematic block diagram of another embodiment of acomputing system in accordance with the present invention;

FIG. 6B is a diagram of an embodiment of a message format in accordancewith the present invention;

FIG. 6C is a schematic block diagram of another embodiment of acomputing system in accordance with the present invention;

FIG. 6D is a flowchart illustrating an example of generating a protocolheader of a dispersed storage network (DSN) frame in accordance with thepresent invention;

FIG. 7A is a diagram illustrating an example of a read request messageformat in accordance with the present invention;

FIG. 7B is a flowchart illustrating an example of generating a readrequest message in accordance with the present invention;

FIG. 8A is a diagram illustrating an example of a read response messageformat in accordance with the present invention;

FIG. 8B is a flowchart illustrating an example of generating a readresponse message in accordance with the present invention;

FIG. 9A is a diagram illustrating an example of a write request messageformat in accordance with the present invention;

FIG. 9B is a flowchart illustrating an example of generating a writerequest message in accordance with the present invention;

FIG. 10A is a diagram illustrating an example of a write responsemessage format in accordance with the present invention;

FIG. 10B is a table illustrating an example of a write response statuscode format in accordance with the present invention;

FIG. 10C is a flowchart illustrating an example of generating a writeresponse message in accordance with the present invention;

FIG. 11A is a diagram illustrating an example of a checked write requestmessage format in accordance with the present invention;

FIG. 11B is a flowchart illustrating an example of generating a checkedwrite request message in accordance with the present invention;

FIG. 12A is a diagram illustrating an example of a checked writeresponse message format in accordance with the present invention;

FIG. 12B is a table illustrating an example of a checked write responsestatus code format in accordance with the present invention;

FIG. 12C is a flowchart illustrating an example of generating a checkedwrite response message in accordance with the present invention;

FIG. 13A is a diagram illustrating an example of a write commit requestmessage format in accordance with the present invention;

FIG. 13B is a flowchart illustrating an example of generating a writecommit request message in accordance with the present invention;

FIG. 14A is a diagram illustrating an example of a write commit responsemessage format in accordance with the present invention;

FIG. 14B is a flowchart illustrating an example of generating a writecommit response message in accordance with the present invention;

FIG. 15A is a diagram illustrating an example of a write rollbackrequest message format in accordance with the present invention;

FIG. 15B is a flowchart illustrating an example of generating a writerollback request message in accordance with the present invention;

FIG. 16A is a diagram illustrating an example of a write rollbackresponse message format in accordance with the present invention;

FIG. 16B is a flowchart illustrating an example of generating a writerollback response message in accordance with the present invention;

FIG. 17A is a diagram illustrating an example of a finalize writerequest message format in accordance with the present invention;

FIG. 17B is a flowchart illustrating an example of generating a finalizewrite request message in accordance with the present invention;

FIG. 18A is a diagram illustrating an example of a finalize writeresponse message format in accordance with the present invention;

FIG. 18B is a flowchart illustrating an example of generating a finalizewrite response message in accordance with the present invention;

FIG. 19A is a diagram illustrating an example of an undo write requestmessage format in accordance with the present invention;

FIG. 19B is a flowchart illustrating an example of generating an undowrite request message in accordance with the present invention;

FIG. 20A is a diagram illustrating an example of an undo write responsemessage format in accordance with the present invention;

FIG. 20B is a flowchart illustrating an example of generating an undowrite response message in accordance with the present invention;

FIG. 21A is a diagram illustrating an example of a check request messageformat in accordance with the present invention;

FIG. 21B is a flowchart illustrating an example of generating a checkrequest message in accordance with the present invention;

FIG. 22A is a diagram illustrating an example of a check responsemessage format in accordance with the present invention;

FIG. 22B is a flowchart illustrating an example of generating a checkresponse message in accordance with the present invention;

FIG. 23A is a diagram illustrating an example of a list range requestmessage format in accordance with the present invention;

FIG. 23B is a flowchart illustrating an example of generating a listrange request message in accordance with the present invention;

FIG. 24A is a diagram illustrating an example of a list range responsemessage format in accordance with the present invention;

FIG. 24B is a flowchart illustrating an example of generating a listrange response message in accordance with the present invention;

FIG. 25A is a diagram illustrating an example of a list digest requestmessage format in accordance with the present invention;

FIG. 25B is a flowchart illustrating an example of generating a listdigest request message in accordance with the present invention;

FIG. 26A is a diagram illustrating an example of a list digest responsemessage format in accordance with the present invention;

FIG. 26B is a flowchart illustrating an example of generating a listdigest response message in accordance with the present invention;

FIGS. 27A-C are schematic block diagrams of an embodiment of a dispersedstorage network (DSN) in accordance with the present invention; and

FIG. 27D is a flowchart illustrating an example of storing data inaccordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of a computing system 10 thatincludes one or more of a first type of user devices 12, one or more ofa second type of user devices 14, at least one distributed storage (DS)processing unit 16, at least one DS managing unit 18, at least onestorage integrity processing unit 20, and a distributed storage network(DSN) memory 22 coupled via a network 24. The network 24 may include oneor more wireless and/or wire lined communication systems; one or moreprivate intranet systems and/or public internet systems; and/or one ormore local area networks (LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of distributed storage (DS) units36 for storing data of the system. Each of the DS units 36 includes aprocessing module and memory and may be located at a geographicallydifferent site than the other DS units (e.g., one in Chicago, one inMilwaukee, etc.). The processing module may be a single processingdevice or a plurality of processing devices. Such a processing devicemay be a microprocessor, micro-controller, digital signal processor,microcomputer, central processing unit, field programmable gate array,programmable logic device, state machine, logic circuitry, analogcircuitry, digital circuitry, and/or any device that manipulates signals(analog and/or digital) based on hard coding of the circuitry and/oroperational instructions. The processing module may have an associatedmemory and/or memory element, which may be a single memory device, aplurality of memory devices, and/or embedded circuitry of the processingmodule. Such a memory device may be a read-only memory, random accessmemory, volatile memory, non-volatile memory, static memory, dynamicmemory, flash memory, cache memory, and/or any device that storesdigital information. Note that if the processing module includes morethan one processing device, the processing devices may be centrallylocated (e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that when the processing module implements one or more ofits functions via a state machine, analog circuitry, digital circuitry,and/or logic circuitry, the memory and/or memory element storing thecorresponding operational instructions may be embedded within, orexternal to, the circuitry comprising the state machine, analogcircuitry, digital circuitry, and/or logic circuitry. Still further notethat, the memory element stores, and the processing module executes,hard coded and/or operational instructions corresponding to at leastsome of the steps and/or functions illustrated in FIGS. 1-26B.

Each of the user devices 12-14, the DS processing unit 16, the DSmanaging unit 18, and the storage integrity processing unit 20 may be aportable computing device (e.g., a social networking device, a gamingdevice, a cell phone, a smart phone, a personal digital assistant, adigital music player, a digital video player, a laptop computer, ahandheld computer, a video game controller, and/or any other portabledevice that includes a computing core) and/or a fixed computing device(e.g., a personal computer, a computer server, a cable set-top box, asatellite receiver, a television set, a printer, a fax machine, homeentertainment equipment, a video game console, and/or any type of homeor office computing equipment). Such a portable or fixed computingdevice includes a computing core 26 and one or more interfaces 30, 32,and/or 33. An embodiment of the computing core 26 will be described withreference to FIG. 2.

With respect to the interfaces, each of the interfaces 30, 32, and 33includes software and/or hardware to support one or more communicationlinks via the network 24 and/or directly. For example, interface 30supports a communication link (wired, wireless, direct, via a LAN, viathe network 24, etc.) between the first second type of user device 14and the DS processing unit 16. As another example, DSN interface 32supports a plurality of communication links via the network 24 betweenthe DSN memory 22 and the DS processing unit 16, the first type of userdevice 12, and/or the storage integrity processing unit 20. As yetanother example, interface 33 supports a communication link between theDS managing unit 18 and any one of the other devices and/or units 12,14, 16, 20, and/or 22 via the network 24.

In general and with respect to data storage, the computing system 10supports three primary functions: distributed network data storagemanagement, distributed data storage and retrieval, and data storageintegrity verification. In accordance with these three primaryfunctions, data can be distributedly stored in a plurality of physicallydifferent locations and subsequently retrieved in a reliable and securemanner regardless of failures of individual storage devices, failures ofnetwork equipment, the duration of storage, the amount of data beingstored, attempts at hacking the data, etc.

The DS managing unit 18 performs distributed network data storagemanagement functions, which include establishing distributed datastorage parameters, performing network operations, performing networkadministration, and/or performing network maintenance. The DS managingunit 18 establishes the distributed data storage parameters (e.g.,allocation of virtual DSN memory space, distributed storage parameters,security parameters, billing information, user profile information,etc.) for one or more of the user devices 12-14 (e.g., established forindividual devices, established for a user group of devices, establishedfor public access by the user devices, etc.). For example, the DSmanaging unit 18 coordinates the creation of a vault (e.g., a virtualmemory block) within the DSN memory 22 for a user device (for a group ofdevices, or for public access). The DS managing unit 18 also determinesthe distributed data storage parameters for the vault. In particular,the DS managing unit 18 determines a number of slices (e.g., the numberthat a data segment of a data file and/or data block is partitioned intofor distributed storage) and a read threshold value (e.g., the minimumnumber of slices required to reconstruct the data segment).

As another example, the DS managing unit 18 creates and stores, locallyor within the DSN memory 22, user profile information. The user profileinformation includes one or more of authentication information,permissions, and/or the security parameters. The security parameters mayinclude one or more of encryption/decryption scheme, one or moreencryption keys, key generation scheme, and data encoding/decodingscheme.

As yet another example, the DS managing unit 18 creates billinginformation for a particular user, user group, vault access, publicvault access, etc. For instance, the DS managing unit 18 tracks thenumber of times a user accesses a private vault and/or public vaults,which can be used to generate a per-access bill. In another instance,the DS managing unit 18 tracks the amount of data stored and/orretrieved by a user device and/or a user group, which can be used togenerate a per-data-amount bill.

The DS managing unit 18 also performs network operations, networkadministration, and/or network maintenance. As at least part ofperforming the network operations and/or administration, the DS managingunit 18 monitors performance of the devices and/or units of thecomputing system 10 for potential failures, determines the devices'and/or units' activation status, determines the devices' and/or units'loading, and any other system level operation that affects theperformance level of the computing system 10. For example, the DSmanaging unit 18 receives and aggregates network management alarms,alerts, errors, status information, performance information, andmessages from the devices 12-14 and/or the units 16, 20, 22. Forexample, the DS managing unit 18 receives a simple network managementprotocol (SNMP) message regarding the status of the DS processing unit16.

The DS managing unit 18 performs the network maintenance by identifyingequipment within the computing system 10 that needs replacing,upgrading, repairing, and/or expanding. For example, the DS managingunit 18 determines that the DSN memory 22 needs more DS units 36 or thatone or more of the DS units 36 needs updating.

The second primary function (i.e., distributed data storage andretrieval) begins and ends with a user device 12-14. For instance, if asecond type of user device 14 has a data file 38 and/or data block 40 tostore in the DSN memory 22, it sends the data file 38 and/or data block40 to the DS processing unit 16 via its interface 30. As will bedescribed in greater detail with reference to FIG. 2, the interface 30functions to mimic a conventional operating system (OS) file systeminterface (e.g., network file system (NFS), flash file system (FFS),disk file system (DFS), file transfer protocol (FTP), web-baseddistributed authoring and versioning (WebDAV), etc.) and/or a blockmemory interface (e.g., small computer system interface (SCSI), internetsmall computer system interface (iSCSI), etc.). In addition, theinterface 30 may attach a user identification code (ID) to the data file38 and/or data block 40.

The DS processing unit 16 receives the data file 38 and/or data block 40via its interface 30 and performs a distributed storage (DS) processthereon (e.g., an error coding dispersal storage function). The DSprocessing 34 begins by partitioning the data file 38 and/or data block40 into one or more data segments, which is represented as Y datasegments. For example, the DS processing 34 may partition the data file38 and/or data block 40 into a fixed byte size segment (e.g., 2¹ to2^(n) bytes, where n=>2) or a variable byte size (e.g., change byte sizefrom segment to segment, or from groups of segments to groups ofsegments, etc.).

For each of the Y data segments, the DS processing 34 error encodes(e.g., forward error correction (FEC), information dispersal algorithm,or error correction coding) and slices (or slices then error encodes)the data segment into a plurality of error coded (EC) data slices 42-48,which is represented as X slices per data segment. The number of slices(X) per segment, which corresponds to a number of pillars n, is set inaccordance with the distributed data storage parameters and the errorcoding scheme. For example, if a Reed-Solomon (or other FEC scheme) isused in an n/k system, then a data segment is divided into n slices,where k number of slices is needed to reconstruct the original data(i.e., k is the threshold). As a few specific examples, the n/k factormay be 5/3; 6/4; 8/6; 8/5; 16/10.

For each EC slice 42-48, the DS processing unit 16 creates a uniqueslice name and appends it to the corresponding EC slice 42-48. The slicename includes universal DSN memory addressing routing information (e.g.,virtual memory addresses in the DSN memory 22) and user-specificinformation (e.g., user ID, file name, data block identifier, etc.).

The DS processing unit 16 transmits the plurality of EC slices 42-48 toa plurality of DS units 36 of the DSN memory 22 via the DSN interface 32and the network 24. The DSN interface 32 formats each of the slices fortransmission via the network 24. For example, the DSN interface 32 mayutilize an internet protocol (e.g., TCP/IP, etc.) to packetize the ECslices 42-48 for transmission via the network 24.

The number of DS units 36 receiving the EC slices 42-48 is dependent onthe distributed data storage parameters established by the DS managingunit 18. For example, the DS managing unit 18 may indicate that eachslice is to be stored in a different DS unit 36. As another example, theDS managing unit 18 may indicate that like slice numbers of differentdata segments are to be stored in the same DS unit 36. For example, thefirst slice of each of the data segments is to be stored in a first DSunit 36, the second slice of each of the data segments is to be storedin a second DS unit 36, etc. In this manner, the data is encoded anddistributedly stored at physically diverse locations to improve datastorage integrity and security. Further examples of encoding the datasegments will be provided with reference to one or more of FIGS. 2-26B.

Each DS unit 36 that receives an EC slice 42-48 for storage translatesthe virtual DSN memory address of the slice into a local physicaladdress for storage. Accordingly, each DS unit 36 maintains a virtual tophysical memory mapping to assist in the storage and retrieval of data.

The first type of user device 12 performs a similar function to storedata in the DSN memory 22 with the exception that it includes the DSprocessing. As such, the user device 12 encodes and slices the data fileand/or data block it has to store. The device then transmits the slices11 to the DSN memory via its DSN interface 32 and the network 24.

For a second type of user device 14 to retrieve a data file or datablock from memory, it issues a read command via its interface 30 to theDS processing unit 16. The DS processing unit 16 performs the DSprocessing 34 to identify the DS units 36 storing the slices of the datafile and/or data block based on the read command. The DS processing unit16 may also communicate with the DS managing unit 18 to verify that theuser device 14 is authorized to access the requested data.

Assuming that the user device 14 is authorized to access the requesteddata, the DS processing unit 16 issues slice read commands to at least athreshold number of the DS units 36 storing the requested data (e.g., toat least 10 DS units for a 16/10 error coding scheme). Each of the DSunits 36 receiving the slice read command, verifies the command,accesses its virtual to physical memory mapping, retrieves the requestedslice, or slices, and transmits it to the DS processing unit 16.

Once the DS processing unit 16 has received a read threshold number ofslices for a data segment, it performs an error decoding function andde-slicing to reconstruct the data segment. When Y number of datasegments has been reconstructed, the DS processing unit 16 provides thedata file 38 and/or data block 40 to the user device 14. Note that thefirst type of user device 12 performs a similar process to retrieve adata file and/or data block.

The storage integrity processing unit 20 performs the third primaryfunction of data storage integrity verification. In general, the storageintegrity processing unit 20 periodically retrieves slices 45, and/orslice names, of a data file or data block of a user device to verifythat one or more slices have not been corrupted or lost (e.g., the DSunit failed). The retrieval process mimics the read process previouslydescribed.

If the storage integrity processing unit 20 determines that one or moreslices is corrupted or lost, it rebuilds the corrupted or lost slice(s)in accordance with the error coding scheme. The storage integrityprocessing unit 20 stores the rebuilt slice, or slices, in theappropriate DS unit(s) 36 in a manner that mimics the write processpreviously described.

FIG. 2 is a schematic block diagram of an embodiment of a computing core26 that includes a processing module 50, a memory controller 52, mainmemory 54, a video graphics processing unit 55, an input/output (IO)controller 56, a peripheral component interconnect (PCI) interface 58,an IO interface 60, at least one IO device interface module 62, a readonly memory (ROM) basic input output system (BIOS) 64, and one or morememory interface modules. The memory interface module(s) includes one ormore of a universal serial bus (USB) interface module 66, a host busadapter (HBA) interface module 68, a network interface module 70, aflash interface module 72, a hard drive interface module 74, and a DSNinterface module 76. Note the DSN interface module 76 and/or the networkinterface module 70 may function as the interface 30 of the user device14 of FIG. 1. Further note that the 10 device interface module 62 and/orthe memory interface modules may be collectively or individuallyreferred to as 10 ports.

The processing module 50 may be a single processing device or aplurality of processing devices. Such a processing device may be amicroprocessor, micro-controller, digital signal processor,microcomputer, central processing unit, field programmable gate array,programmable logic device, state machine, logic circuitry, analogcircuitry, digital circuitry, and/or any device that manipulates signals(analog and/or digital) based on hard coding of the circuitry and/oroperational instructions. The processing module 50 may have anassociated memory and/or memory element, which may be a single memorydevice, a plurality of memory devices, and/or embedded circuitry of theprocessing module 50. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, cache memory, and/or any devicethat stores digital information. Note that if the processing module 50includes more than one processing device, the processing devices may becentrally located (e.g., directly coupled together via a wired and/orwireless bus structure) or may be distributedly located (e.g., cloudcomputing via indirect coupling via a local area network and/or a widearea network). Further note that when the processing module 50implements one or more of its functions via a state machine, analogcircuitry, digital circuitry, and/or logic circuitry, the memory and/ormemory element storing the corresponding operational instructions may beembedded within, or external to, the circuitry comprising the statemachine, analog circuitry, digital circuitry, and/or logic circuitry.Still further note that, the memory element stores, and the processingmodule 50 executes, hard coded and/or operational instructionscorresponding to at least some of the steps and/or functions illustratedin FIGS. 1-26B.

FIG. 3 is a schematic block diagram of an embodiment of a dispersedstorage (DS) processing module 34 of user device 12 and/or of the DSprocessing unit 16. The DS processing module 34 includes a gatewaymodule 78, an access module 80, a grid module 82, and a storage module84. The DS processing module 34 may also include an interface 30 and theDSnet interface 32 or the interfaces 68 and/or 70 may be part of userdevice 12 or of the DS processing unit 16. The DS processing module 34may further include a bypass/feedback path between the storage module 84to the gateway module 78. Note that the modules 78-84 of the DSprocessing module 34 may be in a single unit or distributed acrossmultiple units.

In an example of storing data, the gateway module 78 receives anincoming data object that includes a user ID field 86, an object namefield 88, and the data object field 40 and may also receivecorresponding information that includes a process identifier (e.g., aninternal process/application ID), metadata, a file system directory, ablock number, a transaction message, a user device identity (ID), a dataobject identifier, a source name, and/or user information. The gatewaymodule 78 authenticates the user associated with the data object byverifying the user ID 86 with the DS managing unit 18 and/or anotherauthenticating unit.

When the user is authenticated, the gateway module 78 obtains userinformation from the DS management unit 18, the user device, and/or theother authenticating unit. The user information includes a vaultidentifier, operational parameters, and user attributes (e.g., userdata, billing information, etc.). A vault identifier identifies a vault,which is a virtual memory space that maps to a set of DS storage units36. For example, vault 1 (i.e., user 1's DSN memory space) includeseight DS storage units (X=8 wide) and vault 2 (i.e., user 2's DSN memoryspace) includes sixteen DS storage units (X=16 wide). The operationalparameters may include an error coding algorithm, the width n (number ofpillars X or slices per segment for this vault), a read threshold T, awrite threshold W, an encryption algorithm, a slicing parameter, acompression algorithm, an integrity check method, caching settings,parallelism settings, and/or other parameters that may be used to accessthe DSN memory layer.

The gateway module 78 uses the user information to assign a source name35 to the data. For instance, the gateway module 78 determines thesource name 35 of the data object 40 based on the vault identifier andthe data object. For example, the source name may contain a fileidentifier (ID), a vault generation number, a reserved field, and avault identifier (ID). As another example, the gateway module 78 maygenerate the file ID based on a hash function of the data object 40.Note that the gateway module 78 may also perform message conversion,protocol conversion, electrical conversion, optical conversion, accesscontrol, user identification, user information retrieval, trafficmonitoring, statistics generation, configuration, management, and/orsource name determination.

The access module 80 receives the data object 40 and creates a series ofdata segments 1 through Y 90-92 in accordance with a data storageprotocol (e.g., file storage system, a block storage system, and/or anaggregated block storage system). The number of segments Y may be chosenor randomly assigned based on a selected segment size and the size ofthe data object. For example, if the number of segments is chosen to bea fixed number, then the size of the segments varies as a function ofthe size of the data object. For instance, if the data object is animage file of 4,194,304 eight bit bytes (e.g., 33,554,432 bits) and thenumber of segments Y=131,072, then each segment is 256 bits or 32 bytes.As another example, if segment size is fixed, then the number ofsegments Y varies based on the size of data object. For instance, if thedata object is an image file of 4,194,304 bytes and the fixed size ofeach segment is 4,096 bytes, then the number of segments Y=1,024. Notethat each segment is associated with the same source name.

The grid module 82 receives the data segments and may manipulate (e.g.,compression, encryption, cyclic redundancy check (CRC), etc.) each ofthe data segments before performing an error coding function of theerror coding dispersal storage function to produce a pre-manipulateddata segment. After manipulating a data segment, if applicable, the gridmodule 82 error encodes (e.g., Reed-Solomon, Convolution encoding,Trellis encoding, etc.) the data segment or manipulated data segmentinto X error coded data slices 42-48.

The value X, or the number of pillars (e.g., X=16), is chosen as aparameter of the error coding dispersal storage function. Otherparameters of the error coding dispersal function include a readthreshold T, a write threshold W, etc. The read threshold (e.g., T=10,when X=16) corresponds to the minimum number of error-free error codeddata slices required to reconstruct the data segment. In other words,the DS processing module 34 can compensate for X-T (e.g., 16−10=6)missing error coded data slices per data segment. The write threshold Wcorresponds to a minimum number of DS storage units that acknowledgeproper storage of their respective data slices before the DS processingmodule indicates proper storage of the encoded data segment. Note thatthe write threshold is greater than or equal to the read threshold for agiven number of pillars (X).

For each data slice of a data segment, the grid module 82 generates aunique slice name 37 and attaches it thereto. The slice name 37 includesa universal routing information field and a vault specific field and maybe 48 bytes (e.g., 24 bytes for each of the universal routinginformation field and the vault specific field). As illustrated, theuniversal routing information field includes a slice index, a vault ID,a vault generation, and a reserved field. The slice index is based onthe pillar number and the vault ID and, as such, is unique for eachpillar (e.g., slices of the same pillar for the same vault for anysegment will share the same slice index). The vault specific fieldincludes a data name, which includes a file ID and a segment number(e.g., a sequential numbering of data segments 1-Y of a simple dataobject or a data block number).

Prior to outputting the error coded data slices of a data segment, thegrid module may perform post-slice manipulation on the slices. Ifenabled, the manipulation includes slice level compression, encryption,CRC, addressing, tagging, and/or other manipulation to improve theeffectiveness of the computing system.

When the error coded data slices of a data segment are ready to beoutputted, the grid module 82 determines which of the DS storage units36 will store the EC data slices based on a dispersed storage memorymapping associated with the user's vault and/or DS storage unitattributes. The DS storage unit attributes may include availability,self-selection, performance history, link speed, link latency,ownership, available DSN memory, domain, cost, a prioritization scheme,a centralized selection message from another source, a lookup table,data ownership, and/or any other factor to optimize the operation of thecomputing system. Note that the number of DS storage units 36 is equalto or greater than the number of pillars (e.g., X) so that no more thanone error coded data slice of the same data segment is stored on thesame DS storage unit 36. Further note that EC data slices of the samepillar number but of different segments (e.g., EC data slice 1 of datasegment 1 and EC data slice 1 of data segment 2) may be stored on thesame or different DS storage units 36.

The storage module 84 performs an integrity check on the outboundencoded data slices and, when successful, identifies a plurality of DSstorage units based on information provided by the grid module 82. Thestorage module 84 then outputs the encoded data slices 1 through X ofeach segment 1 through Y to the DS storage units 36. Each of the DSstorage units 36 stores its EC data slice(s) and maintains a localvirtual DSN address to physical location table to convert the virtualDSN address of the EC data slice(s) into physical storage addresses.

In an example of a read operation, the user device 12 and/or 14 sends aread request to the DS processing unit 16, which authenticates therequest. When the request is authentic, the DS processing unit 16 sendsa read message to each of the DS storage units 36 storing slices of thedata object being read. The slices are received via the DSnet interface32 and processed by the storage module 84, which performs a parity checkand provides the slices to the grid module 82 when the parity check wassuccessful. The grid module 82 decodes the slices in accordance with theerror coding dispersal storage function to reconstruct the data segment.The access module 80 reconstructs the data object from the data segmentsand the gateway module 78 formats the data object for transmission tothe user device.

FIG. 4 is a schematic block diagram of an embodiment of a grid module 82that includes a control unit 73, a pre-slice manipulator 75, an encoder77, a slicer 79, a post-slice manipulator 81, a pre-slice de-manipulator83, a decoder 85, a de-slicer 87, and/or a post-slice de-manipulator 89.Note that the control unit 73 may be partially or completely external tothe grid module 82. For example, the control unit 73 may be part of thecomputing core at a remote location, part of a user device, part of theDS managing unit 18, or distributed amongst one or more DS storageunits.

In an example of a write operation, the pre-slice manipulator 75receives a data segment 90-92 and a write instruction from an authorizeduser device. The pre-slice manipulator 75 determines if pre-manipulationof the data segment 90-92 is required and, if so, what type. Thepre-slice manipulator 75 may make the determination independently orbased on instructions from the control unit 73, where the determinationis based on a computing system-wide predetermination, a table lookup,vault parameters associated with the user identification, the type ofdata, security requirements, available DSN memory, performancerequirements, and/or other metadata.

Once a positive determination is made, the pre-slice manipulator 75manipulates the data segment 90-92 in accordance with the type ofmanipulation. For example, the type of manipulation may be compression(e.g., Lempel-Ziv-Welch, Huffman, Golomb, fractal, wavelet, etc.),signatures (e.g., Digital Signature Algorithm (DSA), Elliptic Curve DSA,Secure Hash Algorithm, etc.), watermarking, tagging, encryption (e.g.,Data Encryption Standard, Advanced Encryption Standard, etc.), addingmetadata (e.g., time/date stamping, user information, file type, etc.),cyclic redundancy check (e.g., CRC32), and/or other data manipulationsto produce the pre-manipulated data segment.

The encoder 77 encodes the pre-manipulated data segment 90-92 using aforward error correction (FEC) encoder (and/or other type of erasurecoding and/or error coding) to produce an encoded data segment 94. Theencoder 77 determines which forward error correction algorithm to usebased on a predetermination associated with the user's vault, a timebased algorithm, user direction, DS managing unit direction, controlunit direction, as a function of the data type, as a function of thedata segment 90-92 metadata, and/or any other factor to determinealgorithm type. The forward error correction algorithm may be Golay,Multidimensional parity, Reed-Solomon, Hamming, Bose Ray ChauduriHocquenghem (BCH), Cauchy-Reed-Solomon, or any other FEC encoder. Notethat the encoder 77 may use a different encoding algorithm for each datasegment 90-92, the same encoding algorithm for the data segments 90-92of a data object, or a combination thereof.

The encoded data segment 94 is of greater size than the data segment90-92 by the overhead rate of the encoding algorithm by a factor of X/T,where X is the width or number of slices, and T is the read threshold.In this regard, the corresponding decoding process can accommodate atmost X-T missing EC data slices and still recreate the data segment90-92. For example, if X=16 and T=10, then the data segment 90-92 willbe recoverable as long as 10 or more EC data slices per segment are notcorrupted.

The slicer 79 transforms the encoded data segment 94 into EC data slicesin accordance with the slicing parameter from the vault for this userand/or data segment 90-92. For example, if the slicing parameter isX=16, then the slicer 79 slices each encoded data segment 94 into 16encoded slices.

The post-slice manipulator 81 performs, if enabled, post-manipulation onthe encoded slices to produce the EC data slices. If enabled, thepost-slice manipulator 81 determines the type of post-manipulation,which may be based on a computing system-wide predetermination,parameters in the vault for this user, a table lookup, the useridentification, the type of data, security requirements, available DSNmemory, performance requirements, control unit directed, and/or othermetadata. Note that the type of post-slice manipulation may includeslice level compression, signatures, encryption, CRC, addressing,watermarking, tagging, adding metadata, and/or other manipulation toimprove the effectiveness of the computing system.

In an example of a read operation, the post-slice de-manipulator 89receives at least a read threshold number of EC data slices and performsthe inverse function of the post-slice manipulator 81 to produce aplurality of encoded slices. The de-slicer 87 de-slices the encodedslices to produce an encoded data segment 94. The decoder 85 performsthe inverse function of the encoder 77 to recapture the data segment90-92. The pre-slice de-manipulator 83 performs the inverse function ofthe pre-slice manipulator 75 to recapture the data segment 90-92.

FIG. 5 is a diagram of an example of slicing an encoded data segment 94by the slicer 79. In this example, the encoded data segment 94 includesthirty-two bits, but may include more or less bits. The slicer 79disperses the bits of the encoded data segment 94 across the EC dataslices in a pattern as shown. As such, each EC data slice does notinclude consecutive bits of the data segment 94 reducing the impact ofconsecutive bit failures on data recovery. For example, if EC data slice2 (which includes bits 1, 5, 9, 13, 17, 25, and 29) is unavailable(e.g., lost, inaccessible, or corrupted), the data segment can bereconstructed from the other EC data slices (e.g., 1, 3 and 4 for a readthreshold of 3 and a width of 4).

FIG. 6A is a schematic block diagram of another embodiment of acomputing system that includes a user device 12 and a dispersed storage(DS) unit 36. The user device 12 includes a computing core 26 and adispersed storage network (DSN) interface 32. The computing core 26includes a DS processing 34. The DS unit 36 includes a computing core 26and the DSN interface 32. The user device 12 and the DS unit 36 areoperably coupled via a local area network, a wide area network, theInternet, etcetera to enable the DSN interface 32 of the user device 12and of the DS unit 36 to communicate. The DSN interface 32 of the userdevice 12 and/or of the DS unit 36 generates one or more DSN frames tocommunicate a message 102 therebetween. The DSN frame includes aprotocol header and may further include a payload. A format of the DSNframe is discussed in greater detail with reference to FIG. 6B.

A message 102 may be a request message 104, 108 (e.g., read, write,checked write, write commit, write rollback, write finalize, write undo,check request, list request, and/or list digest request) or a responsemessage 106, 110. For example, user device 12, as a requester, generatesa request message 104, 108 and sends it to DS unit 36. DS unit 36, as aresponder, generates a response message 106, 110 and sends it to userdevice 12. In this example, the DS processing 34 of the user device 12(e.g., the requester) generates a request and outputs the request to theDSN interface 32 of the user device 12. The DSN interface 32 of the userdevice 12 formats the request into the request message 104 (whichincludes a DSN frame or DSN frames) and sends it to the DS unit 36(e.g., the responder). The DSN interface of the DS unit 36 extracts therequest from the request message 104 and provides to the computing core26, which generates a response thereto. The computing core 26 providesthe response to the DSN interface 32 of the DS unit 36, which formatsthe response into the response message 106 (which includes one or moreDSN frames) and sends it to user device 12.

Requester and responder roles may change depending on which device ofthe system initiates the request/response message pair. For example, DSunit 36 (e.g., the requester) generates a request message 108 and sendsit to the user device 12 (e.g., the responder). The user device 12generates a response message 110 and sends it to the DS unit 36. Variousmodules and/or units of the system may utilize the request/responsemessage pairs. In addition, a request may send a request message 104,108 to multiple responders in a series and/or parallel manner as will bediscussed in greater detail with reference to FIG. 6C.

FIG. 6B is a diagram of an embodiment of a response or request messageformatted as a dispersed storage network (DSN) frame. The DSN frameincludes a protocol header 112 and may further include a payload 114.The protocol header 112 includes information to request action and/orprovide status. The payload 114 includes M payload bytes of supplementalinformation utilized in further action and/or in a response related tothe information in the protocol header 112.

In an example, the protocol header 112 includes one or more of aprotocol class field 116, a protocol class version field 118, anoperation code field 120, a request/response field 122, a request numberfield 124, and a payload length field 126. The protocol class field 116contains a number of bytes to specify a sub-protocol identifier toenable a plurality of families of protocols to be utilized. For example,the protocol class field 116 is one byte in length and includes aprotocol class value of 01 hex to signify a first protocol class. Theprotocol class version field 118 contains a number of bytes to specify asub-protocol version associated with the protocol class 116 enabling aplurality of versions of protocols to be utilized with each protocolclass. For example, the protocol class version field is one byte inlength and includes a protocol class version value of 01 hex to signifya first protocol class version.

The operation code field 120 contains a number of bytes to specify anoperation code associated with a requested action providing messageinterpretation instructions to a message target. For example, theoperation code field is one byte in length and includes an operationcode value of a read operation. The request/response field 122 containsa number of bytes to specify whether the message is a request message ora response message. For example, the request/response field 122 is onebyte in length and a one-bit flag of the byte (e.g., a most significantbit of the byte) indicates a response/request value. For example, a flagvalue of zero indicates that the message is a request message and a flagvalue of one indicates that the message is a response message.

The request number field 124 contains a number of bytes to include arequest number value to associate at least one request message with atleast one response message. The request number value may be produced asat least one of a random number, a random number plus a predeterminednumber, and based on a previous request number. For example, the requestnumber field 124 is four bytes in length and includes a request numbervalue of 457 to associate a read request message with a read responsemessage when the previous request number value is 456. As anotherexample, the request number field 124 includes a request number value of5,358 to associate a read response message with a read request messagewhen a request number value of 5,358 is extracted from the read requestmessage.

The payload length field 126 contains a number of bytes to include apayload length value to indicate a number of bytes contained in thepayload 114. The payload length value may be determined based on one ormore of counting bytes of the payload 114, utilizing a predeterminednumber based on one or more of the protocol class value, the protocolclass version value, the operation code value, and the response/requestvalue. For example, the payload length field 126 is four bytes in lengthand includes a payload length value of zero when the operation codevalue is associated with a write rollback response operation and theresponse/request value is associated with a response message. As anotherexample, the payload length field 126 includes a payload length value of104 when the operation code value is associated with a read requestmessage and a predetermined formula of 48n+8 associated with the readrequest message is utilized (e.g., where n=2 corresponding to 2 slicenames).

The payload 114 may be organized into one or more payload fields inaccordance with one or more of the values of the protocol class field116, protocol class version field 118, the operation code field 120, andthe request/response field 122. The one or more payload fields includepayload bytes 0-M, wherein values of the payload bytes 0-M areestablished in accordance with the one or more payload fields. Forexample, the one or more payload fields include slice name fields whenthe payload 114 is associated with a read request DSN frame. As anotherexample, the one or more payload fields include one or more encoded dataslices when the payload 114 is associated with a read response DSNframe. Various methods to generate the fields of the DSN frame and/or togenerate values for the fields are discussed in greater detail withreference to FIGS. 6D-26B.

FIG. 6C is a schematic block diagram of another embodiment of acomputing system that includes a dispersed storage (DS) processing unit16 and dispersed storage network (DSN) memory 22 operable to process aplurality of payload scenarios A-D. The DS processing unit 16 includes aDS processing 34 and a DSN interface 32. The DSN memory 22 includes DSunits 1-4 when dispersed storage error coding parameters include apillar width of 4. The DS processing unit 16 generates one or morerequest DSN frames (e.g., a common DSN frame for the DS units or anindividual frame for each DS unit) wherein each DSN frame includes apayload. The DS processing unit 16 sends the one or more request DSNframes to DS units 1-4. For example, the DS processing unit 16 sends afirst DSN frame that includes a payload 105 to DS unit 1, sends a secondDSN frame that includes a payload 107 to DS unit 2, sends a third DSNframe that includes a payload 109 to DS unit 3, and sends a fourth DSNframe that includes a payload 111 to DS unit 4. Each payload 105-111 maycontain unique data or may contain the same data. As a specific example,the DS processing unit 16 produces a plurality of encoded data slices,generates one or more write request messages that include the pluralityof encoded data slices within one or more write request DSN frames, andsends the one or more write request DSN frames to the DSN memory 22 tofacilitate storing the plurality of encoded data slices in the DS units1-4.

In an example of operation, the DS processing 34 dispersed storage errorencodes data utilizing the dispersed storage error coding parameters toproduce 3 sets of encoded data slices 1_1 through 3_4 (e.g., set oneincludes slices 1-1 through 1_4). The DS processing 34 outputs a writerequest that includes three sets of encoded data slices to the DSNinterface 32. The DSN interface 32 generates at least one write requestDSN frame that includes a payload section, which includes an encodeddata slice(s) of the three sets of encoded data slices. The DSNinterface 32 sends the write request DSN frame(s) to the DS units 1-4.For instance, the DS interface 32 sends the write request DSN frame thatincludes payload 105 to DS unit 1; sends the write request DSN framethat includes payload 107 to DS unit 2; sends the write request DSNframe that includes payload 109 to DS unit 3: and sends the writerequest DSN frame that includes payload 111 to DS unit 4.

The DS processing unit 16 selects an encoded data slice to include ineach of the payloads 105-111 in one of a variety of ways. For example,the DS processing unit 16 selects slices having the same pillar numberto include in a payload (e.g., pillar one slices of the sets of encodeddata slices are included in the payload 105). As another example, DSprocessing unit 16 selects the encoded data slices of a set of encodeddata slices to include in a payload. As yet another example, the DSprocessing unit 16 selects a slice to include in the payload. As afurther example, the DS processing unit 16 selects the encoded dataslices of the three sets of encoded data slices to include in thepayload.

The payload scenarios A-D represent example scenarios indicating whichencoded data slices of the three sets of encoded data slices areincluded in the payloads 105-111. Payload scenario A represents ascenario where the DS processing unit 16 selects all slices of thecorresponding pillar of the three sets of encoded data slices perpayload. For example, the DS processing unit 16 selects slices 1_1, 2_1,and 3_1 of pillar 1 to be included in payload 105, slices 1_2, 2_2, and3_2 of pillar 2 to be included in payload 107, slices 1_3, 2_3, and 3_3of pillar 3 to be included in payload 109, and slices 1_4, 2_4, and 3_4of pillar 4 to be included in payload 111. Payload scenario B representsa scenario where the DS processing unit 16 selects one slice of thecorresponding pillar of the three sets of encoded data slices perpayload. For example, the DS processing unit 16 selects slice 1_1 ofpillar 1 to be included in payload 105, slice 1_2 of pillar 2 to beincluded in payload 107, slice 1_3 of pillar 3 to be included in payload109, and slice 1_4 of pillar 4 to be included in payload 111.

Payload scenario C represents a scenario where the DS processing unit 16selects all encoded data slices of the three sets of encoded data slicesfor all payloads 105-111. For example, the DSN interface 32 selectsslices 1_1, 1_2, 1_3, 1_4, 2_1, 2_2, 2_3, 2_4, 3_1, 3_2, 3_3, and 3_4 tobe included in each payload of payloads 105-111. Payload scenario Drepresents a scenario where the DS processing unit 16 selects one of theencoded data slices of the three sets of encoded data slices for allpayloads 105-111. For example, the DSN interface 32 selects slices 1_1,1_2, 1_3, and 1_4 to be included in each payload of payloads 105-111.

FIG. 6D is a flowchart illustrating an example of generating a protocolheader of a dispersed storage network (DSN) frame. The method begins atstep 128 where a processing module generates values for a protocol classfield, a protocol class version field, and an operation code (opcode)field based on an operational function being communicated by the DSNframe. The operational function includes at least one of a readoperation, a check operation, a list range operation, a write operation,a checked write operation, a commit operation, a rollback operation, afinalize operation, an undo operation, and a list digest operation.

The processing module generates a protocol class value for the protocolclass field by at least one of: retrieving the protocol class value froma protocol class list based on the operational function, utilizing theprotocol class value of a request DSN frame (e.g., a DSN frame thatincludes a request message) when the DSN frame is a response DSN frame(e.g., a DSN frame that includes a response message), retrieving theprotocol class value from a support protocol class list, retrieving theprotocol class value from a unit-module type protocol class list, andextracting the protocol class value from a negotiation result. Forexample, the processing module generates a protocol class value of 01when the protocol class value of a corresponding read request DSN framehas value of 01 and the operational function is a read response.

The method continues at step 130 where the processing module generates aprotocol class version field. The processing module generates a protocolclass version value for the protocol class version field by at least oneof utilizing a most recent protocol class version value, retrieving theprotocol class version value from a protocol class version list based onthe operational function, utilizing the protocol class version value ofa request DSN frame when the DSN frame is a response DSN frame,retrieving the protocol class version value from a support protocolclass version list, retrieving the protocol class version value from aunit-module protocol class version list, and extracting the protocolclass version value from a negotiation result. For example, theprocessing module generates a protocol class version value of 03 basedon retrieving the most recent protocol class version value from thesupport protocol class version list. As another example, the processingmodule initiates a negotiation sequence when a protocol class errormessage is received (e.g., indicating that a present protocol classvalue and/or a present protocol class version value is unacceptable).Such a negotiation sequence includes one or more of generating asupported protocol class message, outputting the supported protocolclass message, receiving a message that includes a supported protocolclass list indicating supported protocol classes and/or protocol classversions, selecting at least one of a supported protocol class value anda protocol class version value from the supported protocol class list,and utilizing the at least one of the supported protocol class value andthe supported protocol class version value.

The method continues at step 132 where the processing module generatesan operation code field that includes an opcode value based on one ormore of an operational function being communicated by the DSN frame, anopcode list, and a predetermination. For example, the processing modulegenerates the operation code field to include an opcode value of 40 hexwhen the operational function being communicated by the DSN frame is aread request operation, the protocol class field value is 01, and theprotocol class version field value is 03.

The method continues at step 134 where the processing module generates arequest/response field to indicate a request message for a requestmessage DSN frame or a response message for a response message DSNframe. For example, the processing module generates the request/responsefield to include a value of zero when the DSN frame is the requestmessage DSN frame. As another example, the processing module generatesthe request/response field to include a value of one when the DSN frameis the response message DSN frame.

The method continues at step 136 where the processing module generates arequest number field that includes a request number value by at leastone of transforming a random number generator output to produce thevalue, transforming a variable reference number to produce the value(e.g., a hash or block cipher encryption of the variable referencenumber which increments by one for each new request number value),adding an increment to a previous request number value to produce thevalue, selecting a predetermined number to produce the value, andutilizing a request number value of a request DSN frame when the DSNframe is a response DSN frame. For example, the processing modulegenerates a request number value of 39,239 in a four byte wide requestnumber field based on the random number generator output. As anotherexample, the processing module generates a request number value of 9,093when the previous request number value is 9,083 and the increment is 10.As yet another example, the processing module generates a request numbervalue of 277 when the request number value of the request DSN frame is277 and the DSN frame is a response DSN frame.

The method continues at step 138 where the processing module arranges,in order, the protocol class field, the protocol class version field,the opcode field, the request/response field, the request number field,and a payload length field to produce the protocol header. The methodcontinues at step 140 where the processing module determines whether theDSN frame is to have a payload based on one or more values of one ormore of the fields of the protocol header. For example, the processingmodule determines that the DSN frame is not to have the payload when theopcode value indicates a write commit response operation. As anotherexample, the processing module determines that the DSN frame is to havethe payload when the opcode value indicates a read request operation.The method branches to step 150 when the processing module determinesthat the DSN frame is not to have the payload. The method continues tostep 142 when the processing module determines that the DSN frame is tohave the payload.

At step 142, the processing module determines the payload as one of arequest payload for a request message DSN frame and a response payloadfor a response message DSN frame. Such a determination may be based onone or more of the operational function, the values for the protocolclass field, the protocol class version field, the request/responsefield, and the opcode field. The method to determine the payload isdiscussed in greater detail with reference to FIGS. 7A-26B.

The method continues at step 144 where the processing module sums anumber of bytes of the payload to produce a value for the payload lengthfield. Alternatively, the processing module determines the valueutilizing one or more of a payload length formula and a fixed value.Such a determination may be based on one or more of the operationalfunction, the values for the protocol class field, the protocol classversion field, the request/response field, and the opcode field. Forexample, the processing module determines to utilize a payload lengthformula of 8T to produce the value as a four byte payload length field,where T is the number of transaction numbers, when the operationalfunction is a write commit request operation. As another example, theprocessing module determines to utilize a fixed value of zero when theoperational function is an undo write response operation. As yet anotherexample, the processing module determines to sum the number of bytes ofthe payload to produce the value as a four byte payload length fieldwhen the operational function is a checked write request operation.

The method continues at step 146 where the processing module appends thepayload to the protocol header to produce the DSN frame. The methodcontinues at step 148 where the processing module outputs the DSN frame.For example, the processing module sends a request message DSN frame toone or more DS unit for a write request operation. As another example,the processing module sends a response message DSN to a requestingdevice that initiated a write request.

The method continues at step 150 where the processing module establishesa value for the payload length field as a predetermined value. Forexample, processing module establishes the value as zero for the payloadfield when the DSN frame is not to have a payload. The method continuesat step 152 where the processing module establishes the protocol headeras the DSN frame. The method continues at step 148 where the processingmodule outputs the DSN frame.

FIG. 7A is a diagram illustrating an example of a read request messageformat as a request dispersed storage network (DSN) frame 154 thatincludes a protocol header 112 and a payload 156. The protocol header112 includes one or more of a protocol class field 116, a protocol classversion field 118, an operation code field 120, a request/response field122, a request number field 124, and a payload length field 126. Forexample, the operation code field 120 includes an operation code valueof 40 hex and the request/response field 122 includes a value of zerowhen the request DSN frame is associated with the read requestoperational function.

The payload 156 includes a transaction number field 158 that includes atransaction number value and one or more slice name fields 1-n thatinclude one or more slice names associated with the transaction numbervalue. The transaction number field 158 may be utilized to associate twoor more request/response DSN frames when a multistep sequence isutilized to accomplish a desired overall function. The transactionnumber value may be based on elapsed seconds since Jan. 1, 1970 UTC withnanosecond, millisecond, and/or seconds of precision when theoperational function is to be completed in a transactional manner andmay be set to zero when the operational function is to be completed in anon-transactional manner (e.g., one step or without regard to concurrentoperational functions). For example, a read request DSN frame and acorresponding response DSN frame may each use the same an eight-bytevalue for the transaction number.

Each slice name of a slice name field 1-n is associated with one or moreencoded data slices, which are to be read and returned in an associatedread response operation. For example, to read encoded data slices 1 and2, the payload 156 includes a transaction number 158 and two 48 bytesslice name fields that includes slice names 1 and slice name 2.

FIG. 7B is a flowchart illustrating an example of generating a readrequest message for a request dispersed storage network (DSN) frame tosupport a read request operation. The method begins at step 160 where aprocessing module generates values for fields of a protocol header. Step160 includes steps 128-130 of FIG. 6D where the processing modulegenerates a protocol class value for a protocol class field andgenerates a protocol class version value for a protocol class versionfield. Such generation of the fields of the protocol header includesgenerating the protocol class field to indicate a protocol class for theread request operation and generating the protocol class version fieldto indicate a protocol class version for the read request operation.

The method continues at step 162, which includes steps 132-134 of FIG.6D, where the processing module generates an operation code field toindicate a read request operation (e.g., an operation code value of 40hex) and generates a request/response value of zero for arequest/response field. The method continues at step 136 of FIG. 6Dwhere the processing module determines a request number value for arequest number field.

The method continues at step 166 where the processing module generates apayload section of the read request DSN frame to include one or moreslice name fields containing one or more slice names. The processingmodule may generate the one or more slice names based on informationreceived in a previous read request, a list, a predetermination, aretrieval command, an error message, and/or a table lookup. For example,the processing module generates five slice names based on receiving aretrieval command that includes the five slice names to retrieve one ormore encoded data slices associated with the five slice names.

The method continues at step 168 where the processing module generates apayload length field of the protocol header to include a payload lengththat represents a length of the payload section. Such generation of thepayload length may include one or more of determining a length of atransaction number, determining a length for each of the one or moreslices names, determining a number of slice names of the one or moreslices names and generating the payload length for the payload lengthfield based on the length of the transaction number, the length for eachof the one or more slices names, and the number of slice names of theone or more slices names.

The method continues at step 170 where the processing module generates atransaction number field of the payload section to include a transactionnumber value corresponding to the read request operation. The methodcontinues at step 172 where the processing module populates the protocolheader and the payload to produce the read request message.

The method continues at step 174 where the processing module outputs therequest DSN frame in order of the protocol header, the transactionnumber field, and the one or more slice name fields. Alternatively, orin addition to, the processing module generates a plurality of DSNframes regarding the read request operation, wherein the plurality ofDSN frames includes the request DSN frame. In addition, the processingmodule may update a slice status table to indicate that the one or moreslice names are associated with a read-lock status to prevent anyfurther modifications of associated encoded data slices until stepsassociated with the read request operation are completed (e.g., encodeddata slices are received in response to the read request message).

FIG. 8A is a diagram illustrating an example of a read responsedispersed storage network (DSN) frame 176 that includes a protocolheader 112 and a payload 178. The protocol header 112 includes one ormore of a protocol class field 116, a protocol class version field 118,an operation code field 120, a request/response field 122, a requestnumber field 124, and a payload length field 126. For example, theoperation code field 120 includes an operation code value of 40 hex andthe request/response field 122 includes a value of one when the responseDSN frame is associated with the read response operational function.

The payload 178 includes one or more slice payload sections 1-n thatcorrespond to one or more slice names 1-n of an associated read requestoperational function (e.g., one or more slice names 1-n extracted from aread request DSN frame). Each slice payload section 1-n includes a slicerevision count field 180, one or more slice revision numbering fields1-r, one or more slice length fields 1-r, and one or more slice payloadfields 1-r, where r represents a slice revision count value of the slicerevision count field 180. The slice revision count value indicates anumber of visible revisions of an associated slice name included in theslice payload section. For example, the slice revision count field isfour bytes in length and includes a slice revision count value of 10when 10 encoded data slices of 10 revisions are visible associated withthe corresponding slice name. As another example, the slice revisioncount value is set to zero when there is no encoded data slice that isassociated with the corresponding slice name (e.g., the slice may havebeen deleted).

Each slice revision numbering field 1-r includes a revision number ofthe associated slice name. For example, a slice revision numbering fieldis eight bytes in length and includes a revision number that is greaterthan other revision numbers of the slice name (e.g., most currentrevision of the slice). Each slice length field 1-r includes a length ofa corresponding encoded data slice. For example, a slice length fieldvalue is set to 4,096 as a number of bytes of the corresponding encodeddata slice. As another example, the slice length field value is set tozero when an encoded data slice of the revision of the correspondingslice name does not exist (e.g., the slice was deleted). Each slicepayload field 1-r includes the corresponding encoded data slice. Theslice payload field may be set to zero if the corresponding encoded dataslice does not exist.

FIG. 8B is a flowchart illustrating an example of generating a readresponse message for a response dispersed storage network (DSN) frame tosupport a read response operation, which include similar steps to FIG.6D. The method begins with step 182 where a processing module generatesfields of a protocol header to include values of the fields of theprotocol header. Step 182 includes steps 128-130 of FIG. 6D where theprocessing module generates a protocol class value for a protocol classfield and generates a protocol class version value for a protocol classversion field. Such generation of the fields of the protocol headerincludes generating the protocol class field to indicate a protocolclass for the read response operation and generating the protocol classversion field to indicate a protocol class version for the read responseoperation.

The method continues at step 184 that includes steps 132-134 of FIG. 6Dwhere the processing module generates an operation code field toindicate a read response operation (e.g., an operation code value of 40hex) and generates a request/response value of one for arequest/response field. The method continues at step 136 of FIG. 6Dwhere the processing module determines a request number value for arequest number field by utilizing a request number value of a requestDSN frame when the DSN frame is a response DSN frame (e.g.,corresponding to the read response operation).

The method continues at step 188 where the processing module generates apayload of the response DSN frame regarding one or more slice names of aread response operation to include one or more slice payload sections,wherein generating a slice payload section of the one or more slicepayload sections of a slice name of the one or more slice names includesgenerating a slice revision count field to indicate a number ofrevisions of the slice name included in the slice payload section andgenerating a slice revision numbering field for each of the revisions ofthe slice name to include a revision number. Such a slice revision countfield may be set to zero when there are no revisions of the slice name(e.g., a deleted encoded data slice).

The method continues at step 190 where the processing module generates aslice length field for each of the revisions of the slice name toinclude a length of a corresponding encoded data slice and generates aslice payload field for each of the revisions of the slice name toinclude the corresponding encoded data slice. The method continues atstep 192 where the processing module generates a payload length field ofthe protocol header to include a payload length that represents a lengthof the one or more slice payload sections. The method continues at step194 where the processing module populates the protocol header and thepayload to produce the read response message.

The method continues at step 196 where the processing module outputs theresponse DSN frame in order of the protocol header, and the one or moreslice payload sections, wherein, within each slice payload section ofthe one or more slice payload sections, in an order of the slicerevision count field, and for each of the revisions of the slice name,the slice revision numbering field, the slice length field, and theslice payload field. In addition, the processing module may establish anerror condition based on one or more of the one or more slice namesbeing associated with a locked encoded data slice state, a transactionnumber error (e.g., a slice name is locked by a second transactionnumber different from any transaction number associated with acorresponding read request message), the one or more slice names areassociated with one or more encoded data slices that are not locallystored (e.g., a wrong DSN address), and a read request message is notauthorized (e.g., a requester is not authorized to access such a portionof a DSN). The processing module discards the response DSN frame whenthe error condition is established.

FIG. 9A is a diagram illustrating an example of a write requestdispersed storage network (DSN) frame 200 that includes a protocolheader 112 and a payload 202. The protocol header 112 includes one ormore of a protocol class field 116, a protocol class version field 118,an operation code field 120, a request/response field 122, a requestnumber field 124, and a payload length field 126. For example, theoperation code field 120 includes an operation code value of 50 hex andthe request/response field 122 includes a value of zero when the requestDSN frame corresponds to an associated write request operationalfunction.

The payload 202 includes a transaction number field 158 and one or moreslice payload sections 1-n associated with the transaction number. Eachslice payload section 1-n corresponds to a slice name 1-n of theassociated write request operational function and includes a slice namefield, a slice revision numbering field, a slice length field, and aslice payload field. For example, a slice payload section 1 includesslice name field 1, slice revision numbering field 1, slice length field1, and slice payload field 1, and a slice payload section 2 includesslice name field 2, slice revision numbering field 2, slice length field2, slice payload field 2 when two slice names are associated with thewrite request operational function (e.g., two encoded data slices towrite).

The slice name field includes a slice name 1-n of the associated writerequest operational function. The slice revision numbering fieldincludes a revision number of a corresponding encoded data slice of theslice name. The slice length field includes a length of thecorresponding encoded data slice when the corresponding encoded dataslice is to be stored. The slice length field includes a value of zerowhen the corresponding encoded data slice is to be deleted (e.g., thecorresponding encoded data slice is a previously stored encoded dataslice). The slice payload field includes the corresponding encoded dataslice when the corresponding encoded data slice is to be stored.

FIG. 9B is a flowchart illustrating an example of generating a writerequest message for a dispersed storage network (DSN) frame to support awrite request operation, which include similar steps to FIGS. 6D and 7B.The method begins with step 204 where a processing module generatesfields of a protocol header to include values of the fields of theprotocol header. Step 204 includes steps 128-130 of FIG. 6D where theprocessing module generates a protocol class value for a protocol classfield and generates a protocol class version value for a protocol classversion field. Such generation of the fields of the protocol headerincludes generating the protocol class field to indicate a protocolclass for the write request operation and generating the protocol classversion field to indicate a protocol class version for the write requestoperation.

The method continues at step 206 that includes steps 132-134 of FIG. 6Dwhere the processing module generates an operation code field toindicate the write request operation (e.g., an operation code value of50 hex) and generates a request/response value of zero for arequest/response field (e.g., indicating a request message). The methodcontinues at step 136 of FIG. 6D where the processing module determinesa request number value for a request number field.

The method continues at step 210 where the processing module generatesone or more payload sections of the request DSN frame regarding thewrite request operation. Such generation of a slice payload section ofthe one or more slice payload sections includes generating a slice namefield to include a slice name of one or more slice names correspondingto an encoded data slice of one or more encoded data slices, generatinga slice revision numbering field to include a revision number of theslice name, generating a slice length field to include a length of theencoded data slice, and generating a slice payload field to include theencoded data slice.

The method continues at step 170 of FIG. 7B where the processing moduledetermines a transaction number field of the payload to include atransaction number corresponding to the write request operation. Themethod continues at step 212 where the processing module generates apayload length field of the protocol header to include a payload lengththat represents length of the transaction number field and length of theone or more slice payload sections. Such a length of a slice payloadsection of the one or more slice payload sections includes a length ofthe slice name field, a length of the slice revision numbering field, alength of the slice length field, and a length of the slice payloadfield.

The method continues at step 216 where the processing module populatesthe protocol header and the payload to produce the write requestmessage. The method continues at step 218 where the processing moduleoutputs the request DSN frame in order of the protocol header, thetransaction number field, and the one or more slice payload sections.Alternatively, or in addition to, the processing module generates aplurality of DSN frames regarding the write request operation, whereinthe plurality of DSN frames includes the request DSN frame. In addition,the processing module may update a slice status table to indicate thatthe one or more slice names are associated with a write-lock status toprevent any modifications of the associated encoded data slices untilsteps associated with the write request operation are completed (e.g., afavorable number of write commit response messages have been receivedassociated with the write request operation).

FIG. 10A is a diagram illustrating an example of a write responsedispersed storage network (DSN) frame 220 that includes a protocolheader 112 and a payload 222. The protocol header 112 includes one ormore of a protocol class field 116, a protocol class version field 118,an operation code field 120, a request/response field 122, a requestnumber field 124, and a payload length field 126. For example, theoperation code field 120 includes an operation code value of 50 hex andthe request/response field 122 includes a value of one when the responseDSN frame is associated with the write response operational function.

The payload 222 includes one or more status fields 1-n, wherein eachstatus field of the one or more status fields 1-n includes a status coderegarding storing of an encoded data slice associated with a slice nameof one or more slice names (e.g., n slice names) of the write responseoperation. The write response message 220 may be generated in responseto receiving a write request message. For example, status field 1corresponds to a slice name 1 of the write request message, status field2 corresponds to slice name 2 of the write request message, etc. Thestatus code may be generated in accordance with a write response statuscode format, wherein the write response status code format indicates adisposition of the storing of the encoded data slice.

FIG. 10B is a table illustrating an example of a write response statuscode format table that includes a write response status code formatdescription field 224 and a status code field 226. The write responsestatus code format description field 224 includes one or moredispositions of storing of an encoded data slice and the status codefield 226 includes one or more corresponding status codes. Such a statuscode of the one or more corresponding status codes is included in anassociated status field of a write response message. In an example ofoperation, a processing module associated with a dispersed storage (DS)unit receives a write request message from a requester, determines adisposition of storing an encoded data slice associated with the writerequest message, matches the disposition to an entry of the writeresponse status code format description field 224, generates a writeresponse message that includes a corresponding status code of the statuscode field 226, and sends the write response message to the requester.

In an instance of generating a status code, a status code of 00 hex isgenerated when a write sequence associated with the encoded data slicesucceeded with no errors. In another instance, a status code of 01 hexis generated when the encoded data slice is associated with a lockedstatus by another transaction (e.g., a transaction conflict wherein atransaction number received in a write request message does not match atransaction number associated with a pending operation that invoked thelocked status). In another instance, a status code of 02 hex isgenerated when a slice name associated with the encoded data slice isnot associated with an assigned slice name range (e.g., an addressingerror). In yet another instance, a status code of 03 hex is generatedwhen the slice name associated with the encoded data slice does not meetcriteria for a checked operation (e.g., a last known revision of theslice name is not present). In another instance, a status code of 04 hexis generated when the write request message is unauthorized.

FIG. 10C is a flowchart illustrating an example of generating a writeresponse message for a response dispersed storage network (DSN) frame tosupport a write response operation, which includes similar steps to FIG.6D. The method begins at step 228 where a processing module generatesfields of a protocol header to include values of the fields of theprotocol header. Step 228 includes steps 128-130 of FIG. 6D where theprocessing module generates a protocol class value for a protocol classfield and generates a protocol class version value for a protocol classversion field. Such generation of the fields of the protocol headerincludes generating the protocol class field to indicate a protocolclass for the write response operation and generating the protocol classversion field to indicate a protocol class version for the writeresponse operation.

The method continues at step 230 that includes steps 132-134 of FIG. 6Dwhere the processing module generates an operation code field toindicate a write response operation (e.g., an operation code value of 50hex) and generates a request/response value of one for arequest/response field to indicate a response message. The methodcontinues at step 136 of FIG. 6D where the processing module determinesa request number value for a request number field.

The method continues at step 234 where the processing module generates apayload of the response DSN frame regarding one or more slice names ofthe write response operation to include one or more status fields,wherein generating a status field of the one or more status fields toindicate a status code regarding storing of an encoded data sliceassociated with a slice name of the one or more slice names. Such astatus code includes one of an indication that the encoded data slicewas successfully stored, an indication of a transaction conflict, anindication of an addressing error, an indication that a correspondingwrite request message is unauthorized and an indication that the encodeddata slice was not stored.

The method continues at step 236 where the processing module generates apayload length field of the protocol header to include a payload lengththat represents a length of the one or more status fields. For example,the processing module generates the payload length field to include apayload length of five when a length each of the one or more statusfields is one byte each and there are five status codes included in thepayload of the response DSN frame. The method continues at step 238where the processing module populates the protocol header and thepayload to produce the write response message. The method continues atstep 240 where the processing module outputs the response DSN frame inorder of the protocol header and the one or more status fields, whereinthe order of the one or more status fields corresponds to an order ofslice names of the corresponding write request message.

FIG. 11A is a diagram of an example of a checked write request dispersedstorage network (DSN) frame 242 that includes a protocol header 112 anda payload 244. The protocol header 112 includes one or more of aprotocol class field 116, a protocol class version field 118, anoperation code field 120, a request/response field 122, a request numberfield 124, and a payload length field 126. For example, the operationcode field 120 includes an operation code value of 51 hex and therequest/response field 122 includes a value of zero when the request DSNframe corresponds to the checked write request operational function.

The payload 244 includes a transaction number field 158 and one or moreslice payload sections 1-n associated with a transaction number value ofthe transaction number field 158. Such one or more slice payloadsections 1-n correspond to one or more slice names 1-n of the associatedchecked write request operational function. Each slice payload sectionof the one or more slice payload sections 1-n includes a slice namefield, a last known slice revision numbering field, a new slice revisionnumbering field, a slice length field, and a slice payload field. Forexample, a slice payload section 1 includes slice name field 1, lastknown slice revision numbering field 1, new slice revision numberingfield 1, slice length field 1, and slice payload field 1, and a slicepayload section 2 includes slice name field 2, last known slice revisionnumbering field 2, new slice revision numbering field 2, slice lengthfield 2, slice payload field 2 when two slice names are associated withthe checked write request operational function (e.g., two encoded dataslices to write).

Each of the slice name field includes a slice name 1-n of the associatedchecked write request operational function. The last known slicerevision numbering field includes a last known revision number of apreviously stored encoded data slice of the slice name. The new slicerevision numbering field includes a new revision number of acorresponding encoded data slice (e.g., in the payload of the checkedwrite request message) of the slice name. The slice length fieldincludes a length of the corresponding encoded data slice when thecorresponding encoded data slice is to be stored. The slice length fieldincludes a value of zero when the previously stored encoded data sliceis to be deleted. The slice payload field includes the correspondingencoded data slice when the corresponding encoded data slice is to bestored.

FIG. 11B is a flowchart illustrating an example of generating a checkedwrite request message for a request dispersed storage network (DSN)frame to support a checked write request operation, which includesimilar steps to FIGS. 6D and 7B. The method begins with step 246 wherea processing module generates fields of a protocol header to includevalues of the fields of the protocol header. Step 246 includes steps128-130 of FIG. 6D where the processing module generates a protocolclass value for a protocol class field and generates a protocol classversion value for a protocol class version field. Such generation of thefields of the protocol header includes generating the protocol classfield to indicate a protocol class for the checked write requestoperation and generating the protocol class version field to indicate aprotocol class version for the checked write request operation.

The method continues at step 248 that includes steps 132-134 of FIG. 6Dwhere the processing module generates an operation code field toindicate the checked write request operation (e.g., an operation codevalue of 51 hex) and generates a request/response value of zero for arequest/response field (e.g., indicating a request message). The methodcontinues at step 136 of FIG. 6D where the processing module determinesa request number value for a request number field.

The method continues at step 252 where the processing module generatesone or more payload sections of the request DSN frame regarding thechecked write request operation. The generation of a slice payloadsection includes generating a slice name field to include a slice nameof one or more slice names corresponding to an encoded data slice,generating a last known slice revision numbering field to include a lastknown revision number of the slice name, generating a new slice revisionnumbering field to include a new revision number of the slice namecorresponding to the checked write request operation, generating a slicelength field to include a length of the encoded data slice, andgenerating a slice payload field to include the encoded data slice.

The generation of the last known revision number includes selecting thelast known revision number from a revision number list (e.g., select amost recent revision from a local directory cache), extracting the lastknown slice revision number from a check response message (e.g., a queryresponse of the most recent revision number), and/or extracting the lastknown slice revision number from a read response message (e.g., the mostrecent revision number). The method continues at step 170 of FIG. 7Bwhere the processing module determines a transaction number field of thepayload to include a transaction number corresponding to the checkedwrite request operation.

The method continues at step 256 where the processing module generates apayload length field of the protocol header to include a payload lengththat represents length of the transaction number field and length of theone or more slice payload sections. The length of a slice payloadsection includes a length of the slice name field, a length of the lastknown slice revision numbering field, a length of the new slice revisionnumbering field, a length of the slice length field, and a length of theslice payload field.

The method continues at step 258 where the processing module populatesthe protocol header and the payload to produce the checked write requestmessage. The method continues at step 260 where the processing moduleoutputs the request DSN frame in order of the protocol header, thetransaction number field, and the one or more slice payload sections.Alternatively, or in addition to, the processing module generates aplurality of DSN frames regarding the checked write request operation,wherein the plurality of DSN frames includes the request DSN frame. Inaddition, the processing module may update a slice status table toindicate that the one or more slice names are associated with awrite-lock status to prevent any modifications of the associated encodeddata slices until steps associated with the write request operation arecompleted (e.g., a favorable number of write commit response messageshave been received associated with the write request operation).

FIG. 12A is a diagram of an example of a checked write responsedispersed storage network (DSN) frame 262 that includes a protocolheader 112 and a payload 264. The protocol header 112 includes one ormore of a protocol class field 116, a protocol class version field 118,an operation code field 120, a request/response field 122, a requestnumber field 124, and a payload length field 126. For example, theoperation code field 120 includes an operation code value of 51 hex andthe request/response field 122 includes a value of one when the responseDSN frame is associated with the checked write response operationalfunction.

The payload 264 includes one or more status fields 1-n, wherein eachstatus field includes a status code regarding storing of an encoded dataslice associated with a slice name of one or more slice names (e.g., nslice names). For example, status field 1 corresponds to a slice name 1of the checked write request message, status field 2 corresponds toslice name 2 of the checked write request message, etc. The status codemay be generated in accordance with a checked write response status codeformat, which indicates a disposition of the storing of the encoded dataslice.

FIG. 12B is a table illustrating an example of a checked write responsestatus code format that includes a checked write response status codeformat description field 265 and a status code field 226. The checkedwrite response status code format description field 265 includes one ormore dispositions of storing of an encoded data slice and the statuscode field 226 includes one or more corresponding status codes. In anexample of operation, a processing module associated with a dispersedstorage (DS) unit receives a checked write request message from arequester, determines a disposition of storing an encoded data sliceassociated with the checked write request message, matches thedisposition to an entry of the checked write response status code formatdescription field 265, generates a checked write response message thatincludes a corresponding status code in the status code field 226, andsends the checked write response message to the requester.

In an instance of generating a status code, a status code of 00 hex isgenerated when a checked write sequence associated with the encoded dataslice succeeded with no errors. In another instance, a status code of 01hex is generated when the encoded data slice is associated with a lockedstatus by another transaction (e.g., a transaction conflict wherein atransaction number received in a checked write request message does notmatch a transaction number associated with a pending operation thatinvoked the locked status). In a further instance, a status code of 02hex is generated when a slice name associated with the encoded dataslice is not associated with an assigned slice name range (e.g., anaddressing error). In yet another instance, a status code of 03 hex isgenerated when the slice name associated with the encoded data slicedoes not meet criteria for a checked operation (e.g., a last knownrevision of the slice name is not present). In still another instance, astatus code of 04 hex is generated when the checked write requestmessage is unauthorized.

FIG. 12C is a flowchart illustrating an example of generating a checkedwrite response message for a response dispersed storage network (DSN)frame to support a checked write response operation, which includesimilar steps to FIGS. 6D and 10C. The method begins with step 268 wherea processing module generates fields of a protocol header to includevalues of the fields of the protocol header. Step 268 includes steps128-130 of FIG. 6D where the processing module generates a protocolclass value for a protocol class field and generates a protocol classversion value for a protocol class version field. The generation of thefields of the protocol header includes generating the protocol classfield to indicate a protocol class for the checked write responseoperation and generating the protocol class version field to indicate aprotocol class version for the checked write response operation.

The method continues at step 270, which includes steps 132-134 of FIG.6D, where the processing module generates an operation code field toindicate a write response operation (e.g., an operation code value of 51hex) and generates a request/response value of one for arequest/response field to indicate a response message. The methodcontinues at step 136 of FIG. 6D where the processing module determinesa request number value for a request number field.

The method continues at step 274 where the processing module generates apayload of the response DSN frame regarding one or more slice names ofthe checked write response operation to include one or more statusfields, wherein generating a status field of the one or more statusfields to indicate a status code regarding storing of an encoded dataslice associated with a slice name of the one or more slice names. Astatus code includes an indication that the encoded data slice wassuccessfully stored, a transaction conflict, an addressing error, arevision check error (e.g., a last known revision number received in achecked write request message is not substantially the same as a latestrevision number of the slice name), a corresponding write requestmessage is unauthorized, and/or the encoded data slice was not stored.

The method continues with step 236 of FIG. 10C where the processingmodule generates a payload length field of the protocol header toinclude a payload length that represents a length of the one or morestatus fields. The method continues at step 278 where the processingmodule populates the protocol header and the payload to produce thechecked write response message. The method continues at step 280 wherethe processing module outputs the response DSN frame in order of theprotocol header and the one or more status fields, wherein the order ofthe one or more status fields corresponds to an order of slice names ofthe corresponding checked write request message.

FIG. 13A is a diagram illustrating an example of a write commit requestDSN frame 282 that protocol header 112 and a payload 284. The writecommit request is one of an intermediate write request operations thatis generated subsequent to the generation of a write request operationor a checked write request operation and precedes the generation of aconclusive write request operation (e.g., a finalize write requestoperational function, an undo write request operational function). Theprotocol header 112 includes one or more of a protocol class field 116,a protocol class version field 118, an operation code field 120, arequest/response field 122, a request number field 124, and a payloadlength field 126. For example, the operation code field 120 includes anoperation code value of 21 hex and the request/response field 122includes a value of zero when the request DSN frame corresponds to thewrite commit request operational function.

The payload 284 includes one or more transaction number fields 1-T thatincludes one or more transaction numbers corresponding to the writerequest operation (e.g., the write request operation that precedes thewrite commit request operation). For example, the payload 284 includes 2transaction number fields, where the first transaction number fieldincludes a transaction number of 314 for the write operation and thesecond transaction number field includes a transaction number of 647 forthe write commit operation.

FIG. 13B is a flowchart illustrating an example of generating a writecommit request DSN frame, which includes similar steps to FIG. 6D. Themethod begins at step 286 where a processing module generates fields ofa protocol header to include values of the fields of the protocolheader. Step 286 includes steps 128-130 of FIG. 6D where the processingmodule generates a protocol class value for a protocol class field andgenerates a protocol class version value for a protocol class versionfield. The generation of the fields of the protocol header includesgenerating the protocol class field to indicate a protocol class for thewrite commit request operation and generating the protocol class versionfield to indicate a protocol class version for the write commit requestoperation.

The method continues at step 288 that includes steps 132-134 of FIG. 6Dwhere the processing module generates an operation code field toindicate a write commit request operation (e.g., an operation code valueof 21 hex) and generates a request/response value of zero for arequest/response field (e.g., indicating a request message). The methodcontinues at step 136 of FIG. 6D where the processing module determinesa request number value for a request number field.

The method continues at step 292 where the processing module generates apayload of the request DSN frame by generating one or more transactionnumber fields to include one or more transaction numbers correspondingto a write request operation. The generation of a transaction numberincludes receiving the transaction number (e.g., included in a command)and/or selecting the transaction number from a transaction number list(e.g., the transaction number list includes transaction numbersassociated with the write request operation). For example, theprocessing module selects the transaction number from the transactionnumber list when the one or more transaction numbers are associated withone or more successful write request operations (e.g., favorable writeresponse messages were received corresponding to a write thresholdnumber of encoded data slices per data segment associated with the oneor more transaction numbers).

The method continues at step 294 where the processing module generates aprotocol header of the request DSN frame by generating a payload lengthfield to include a payload length that represents a length of the one ormore transaction number fields. For example, the processing modulegenerates the payload length field to include a payload length oftwenty-four when a length of each of three transaction number fields iseight bytes. The method continues at step 296 where the processingmodule populates the protocol header and the payload to produce thewrite commit request message. The method continues at step 298 where theprocessing module outputs the request DSN frame in order of the protocolheader and the one or more transaction number fields. Alternatively, orin addition to, the processing module generates a plurality of DSNframes regarding the intermediate write request operation, wherein theplurality of DSN frames includes the request DSN frame.

FIG. 14A is a diagram illustrating an example of a write commit responseDSN frame 300 that includes a protocol header 112. The write commitresponse is one of an intermediate write response operation that isgenerated subsequent to the generation of a write request response or achecked write response operation and precedes the generation of aconclusive write response operation.

The protocol header 112 includes one or more of a protocol class field116, a protocol class version field 118, an operation code field 120, arequest/response field 122, a request number field 124, and a payloadlength field 126. For example, the operation code field 120 includes anoperation code value of 21 hex, the request/response field 122 includesa value of one, the request number field 124 includes a request numberextracted from an associated write commit request message, and thepayload length field 126 includes a value of zero when the response DSNframe is associated with the write commit response operational function.

In an operational example, the write commit response message 300 isgenerated and outputted in response to receiving and processing anassociated write commit request message when all transactions associatedwith the write commit request message are successfully committed (e.g.,a slice status table is updated to indicate that one or more slice namesare associated with visible encoded data slices, wherein the one or moreslice names are associated with a transaction number of the write commitrequest message).

FIG. 14B is a flowchart illustrating an example of generating a writecommit response DSN frame, which includes similar steps to FIG. 6D. Themethod begins at step 302, which includes steps 128-130 of FIG. 6D,where the processing module generates a protocol class value for aprotocol class field and generates a protocol class version value for aprotocol class version field. The generation of the fields of theprotocol header includes generating the protocol class field to indicatea protocol class for the intermediate write response operation (e.g.,the write commit response operation) and generating the protocol classversion field to indicate a protocol class version for the intermediatewrite response operation.

The method continues at step 304, which includes steps 132-134 of FIG.6D, where the processing module generates an operation code field toindicate the intermediate write response operation (e.g., the writecommit request operation associated with an operation code value of 21hex) and the processing module generates a request/response value of onefor a request/response field (e.g., indicating a response message). Themethod continues with step 136 of FIG. 6D, where the processing moduledetermines a request number value for a request number field. Forexample, the processing module determines the request number byextracting a request number from a message of an associated intermediatewrite request operation. For instance, the processing module determinesthe request number by extracting a request number from an associatedwrite commit request message.

The method continues at step 308 where the processing module generates apayload length field of the protocol header to include a predeterminedpayload length value. For example, the processing module generates thepayload length field to include a payload length of zero when thepayload length field is associated with the intermediate write responsemessage. The method continues at step 310 where the processing modulepopulates the protocol header to produce the write commit responsemessage. The method continues at step 312 where the processing moduleoutputs in order, the protocol class field, the protocol class versionfield, the operation code field, the request/response field, the requestnumber field, and the payload length field as the response DSN frame ofthe write commit response message.

FIG. 15A is a diagram illustrating an example of a write rollbackrequest DSN frame 314, which is another intermediate write requestoperation. The write rollback request frame 314 includes a protocolheader 112 and a payload 316. The protocol header 112 includes aprotocol class field 116, a protocol class version field 118, anoperation code field 120, a request/response field 122, a request numberfield 124, and/or a payload length field 126. For example, the operationcode field 120 includes an operation code value of 22 hex and therequest/response field 122 includes a value of zero when the request DSNframe corresponds to the write rollback request operational function.

The payload 316 includes one or more transaction number fields 1-T thatinclude one or more transaction numbers corresponding to a write requestoperation. For example, the payload 316 includes a transaction numberfield 1, wherein the transaction number field 1 includes a transactionnumber of 647 when a write rollback request operational function isactive for encoded data slices associated with the transaction number647.

FIG. 15B is a flowchart illustrating an example of generating a writerollback request message for a request dispersed storage network (DSN)frame, which includes similar steps to FIGS. 6D and 13B. The methodbegins at step 318 where a processing module generates fields of aprotocol header to include values therein. Step 318 includes steps128-130 of FIG. 6D where the processing module generates a protocolclass value for a protocol class field and generates a protocol classversion value for a protocol class version field. The generation of thefields of the protocol header includes generating the protocol classfield to indicate a protocol class for the write rollback requestoperation and generating the protocol class version field to indicate aprotocol class version for the write rollback request operation.

The method continues at step 320, which includes steps 132-134 of FIG.6D, where the processing module generates an operation code field toindicate a write rollback request operation (e.g., an operation codevalue of 22 hex) and generates a request/response value of zero for arequest/response field (e.g., indicating a request message). The methodcontinues at step 136 of FIG. 6D where the processing module determinesa request number value for a request number field.

The method continues at step 324 where the processing module generates apayload of the request DSN frame regarding the intermediate writerequest operation by generating one or more transaction number fields ofthe payload to include one or more transaction numbers corresponding toa write request operation. The method continues at step 294 of FIG. 13Bwhere the processing module generates a protocol header of the requestDSN frame by generating a payload length field of the protocol header toinclude a payload length that represents a length of the one or moretransaction number fields.

The method continues at step 328 where the processing module populatesthe protocol header and the payload to produce the write rollbackrequest message. The method continues at step 330 where the processingmodule outputs the request DSN frame in order of the protocol header andthe one or more transaction number fields. Alternatively, or in additionto, the processing module generates a plurality of DSN frames regardingthe intermediate write request operation, wherein the plurality of DSNframes includes the request DSN frame. Alternatively, or in addition to,the processing module updates a slice status table to indicate thatassociated encoded data slices (e.g., of the write request operation)are associated with a write-lock status at a rollback stage to preventany further modifications of the encoded slices until the write rollbackrequest operation concludes (e.g., a corresponding write rollbackresponse message is received).

FIG. 16A is a diagram illustrating an example of a write rollbackresponse DSN frame, which is another intermediate write responseoperation. The response DSN frame 332 includes a protocol header 112,which includes one or more of a protocol class field 116, a protocolclass version field 118, an operation code field 120, a request/responsefield 122, a request number field 124, and a payload length field 126.For example, the operation code field 120 includes an operation codevalue of 22 hex, the request/response field 122 includes a value of one,the request number field 124 includes a request number extracted from anassociated write rollback request message, and the payload length field126 includes a value of zero when the response DSN frame is associatedwith the write rollback response operational function.

In an operational example, the write rollback response message 332 isgenerated and outputted in response to receiving and processing anassociated write rollback request message when the transactionsassociated with the write rollback request message are successfullyrolled back. For example, encoded data slices associated with atransaction number of the write rollback request message are deleted.

FIG. 16B is a flowchart illustrating an example of generating a writerollback response DSN frame, which includes similar steps to FIGS. 6Dand 14B. The method begins with step 334 where a processing modulegenerates fields of a protocol header to include values of the fields ofthe protocol header. Step 334 includes steps 128-130 of FIG. 6D wherethe processing module generates a protocol class value for a protocolclass field and generates a protocol class version value for a protocolclass version field. Such generation of the fields of the protocolheader includes generating the protocol class field to indicate aprotocol class for the intermediate write response operation (e.g., thewrite rollback response operation) and generating the protocol classversion field to indicate a protocol class version for the intermediatewrite response operation.

The method continues at step 336 that includes steps 132-134 of FIG. 6Dwhere the processing module generates an operation code field toindicate the intermediate write response operation (e.g., the writerollback response operation associated with an operation code value of22 hex) and the processing module generates a request/response value ofone for a request/response field (e.g., indicating a response message).The method continues with step 136 of FIG. 6D, where the processingmodule determines a request number value for a request number field(e.g., the processing module determines the request number by extractinga request number from an associated write rollback request message).

The method continues with step 308 of FIG. 14B where the processingmodule generates a payload length field of the protocol header toinclude a predetermined payload length value (e.g., zero for theintermediate write response message). The method continues at step 342where the processing module populates the protocol header to produce thewrite rollback response message. The method continues at step 344 wherethe processing module outputs in order, the protocol class field, theprotocol class version field, the operation code field, therequest/response field, the request number field, and the payload lengthfield as the response DSN frame of the write rollback response message.Alternatively, or in addition to, the processing module may delete oneor more encoded data slices associated with the one or more transactionnumbers of the slice upon receiving the associated write rollbackrequest message.

FIG. 17A is a diagram illustrating an example of a DSN frame 346 for afinalize write request, which is one of conclusive write requestoperations. The request DSN frame 346 includes a protocol header 112 anda payload 348. The protocol header 112 includes one or more of aprotocol class field 116, a protocol class version field 118, anoperation code field 120, a request/response field 122, a request numberfield 124, and a payload length field 126. For example, the operationcode field 120 includes an operation code value of 23 hex and therequest/response field 122 includes a value of zero when the request DSNframe corresponds to the finalize write request operational function.The payload 348 includes one or more slice name fields 1-n, each ofwhich includes a slice name, and one or more slice revision numberingfields 1-n, each of which includes a slice revision number.

FIG. 17B is a flowchart illustrating an example of generating a finalizewrite request DSN frame, which includes similar steps to FIG. 6D. Themethod begins at step 350 where a processing module generates fields ofa protocol header to include corresponding values. Step 350 includessteps 128-130 of FIG. 6D where, when a threshold number of write commitresponses have been received, the processing module generates a protocolclass value for a protocol class field and generates a protocol classversion value for a protocol class version field. The protocol classfield value indicates a protocol class of the finalize write requestoperation and the protocol class version value indicates a protocolclass version for the finalize write request operation.

The method continues at step 352, which includes steps 132-134 of FIG.6D, where the processing module generates an operation code field toindicate a finalize write request operation (e.g., an operation codevalue of 23 hex) and generates a request/response value of zero for arequest/response field (e.g., indicating a request message) when thethreshold number of the one or more write commit responses have beenreceived. The method continues at step 136 of FIG. 6D where theprocessing module determines a request number value for a request numberfield.

The method continues at step 356 where the processing module generates apayload of the request DSN frame to include one or more slice namefields. A slice name field includes a slice name corresponding to awrite commit response of a write request operation.

The method continues at step 358 where the processing module generates apayload length field of the protocol header to include a payload lengththat represents length of the slice name fields and length of the slicerevision numbering fields. The method continues at step 360 where theprocessing module populates the protocol header and the payload toproduce the finalize write request message.

The method continues at step 362 where the processing module outputs therequest DSN frame that includes the finalize write request message inorder of the protocol header and one or more slice field pairs, whereineach of the one or more slice field pairs includes, in order, a slicename field of the one or more slice name fields and a slice revisionnumbering field of the one or more slice revision numbering fields,wherein the slice revision numbering field is associated with the slicename field.

Alternatively, or in addition to, the processing module generates aplurality of DSN frames regarding the conclusive write requestoperation, wherein the plurality of DSN frames includes the request DSNframe. Alternatively, or in addition to, the processing module updates aslice status table to indicate that slice names of the payload of thefinalize write request message are now not associated with a write-lockstatus since they are now a finalized status and hence a previous writerequest operational function has concluded (e.g., a write transactionhas expired).

FIG. 18A is a diagram illustrating an example of a DSN frame of finalizewrite response, which is one of conclusive write response operations.The finalize write response message 364 includes a protocol header 112,which includes one or more of a protocol class field 116, a protocolclass version field 118, an operation code field 120, a request/responsefield 122, a request number field 124, and a payload length field 126.For example, the operation code field 120 includes an operation codevalue of 23 hex, the request/response field 122 includes a value of one,the request number field 124 includes a request number extracted from anassociated finalize write request message, and the payload length field126 includes a value of zero when the response DSN frame is associatedwith the finalize write response operational function.

In an operational example, the finalize write response message 364 isgenerated and outputted in response to receiving and processing anassociated finalize write request message when encoded data slicescorresponding to the finalize write request message are successfullyfinalized (e.g., a newest revision of an encoded data slice remainsstored while encoded data slices of previous revisions are deleted).

FIG. 18B is a flowchart illustrating an example of generating a finalizewrite response DSN frame, which includes similar steps to FIGS. 6D and14B. The method begins at step 366 where a processing module generatesvalues for inclusion in fields of a protocol header. Step 366 includessteps 128-130 of FIG. 6D where the processing module generates aprotocol class value for a protocol class field and generates a protocolclass version value for a protocol class version field.

The method continues at step 368 that includes steps 132-134 of FIG. 6Dwhere the processing module generates an operation code field toindicate the conclusive write response operation (e.g., the finalizewrite response operation associated with an operation code value of 23hex) and the processing module generates a request/response value of onefor a request/response field (e.g., indicating a response message). Thegenerating of the operation code field includes indicating the finalizewrite response operation or by extracting an operational code from acorresponding conclusive write request message (e.g., from a finalizewrite request message). The method continues with step 136 of FIG. 6D,where the processing module determines a request number value associatedwith the conclusive write request operation (e.g., the processing moduledetermines the request number by extracting a request number from theassociated finalize write request message).

The method continues at step 308 of FIG. 14B where the processing modulegenerates a payload length field of the protocol header to include apredetermined payload length value (e.g., zero for the conclusive writeresponse message). The method continues at step 374 where the processingmodule populates the protocol header to produce the finalize writeresponse message. The method continues at step 376 where the processingmodule outputs in order, the protocol class field, the protocol classversion field, the operation code field, the request/response field, therequest number field, and the payload length field as the response DSNframe of the finalize write response message. Alternatively, or inaddition to, the processing module may delete one or more encoded dataslices associated with all but the most recent revision of each slicename of an associated finalize write request message when the one ormore encoded data slices are not associated with a locked status by theanother open transaction.

FIG. 19A is a diagram illustrating an example of a DSN frame for an undowrite request, which is one of the conclusive write request operations.The request DSN frame 378 includes a protocol header 112 and a payload380. The protocol header 112 includes one or more of a protocol classfield 116, a protocol class version field 118, an operation code field120, a request/response field 122, a request number field 124, and apayload length field 126. For example, the operation code field 120includes an operation code value of 24 hex and the request/responsefield 122 includes a value of zero when the request DSN framecorresponds to the undo write request operational function.

The payload 380 includes one or more slice name fields 1-n, each ofwhich includes a slice name corresponding to a write commit response,and slice revision numbering fields 1-n, each of which includes a slicerevision number corresponding to an associated slice name.

FIG. 19B is a flowchart illustrating an example of generating an undowrite request (DSN) frame, which includes similar steps to FIGS. 6D and17B. The method begins at step 382 where a processing module generatesfields of a protocol header to include values of the fields of theprotocol header. Step 382 includes steps 128-130 of FIG. 6D where theprocessing module generates a protocol class value for a protocol classfield and generates a protocol class version value for a protocol classversion field. Such generation of the fields of the protocol headerincludes generating the protocol class field to indicate a protocolclass for the undo write request operation when a threshold number ofone or more write commit responses have not been received within a timeperiod and generating the protocol class version field to indicate aprotocol class version for the undo write request operation when thethreshold number of the one or more write commit responses have not beenreceived within the time period.

The method continues at step 384, which includes steps 132-134 of FIG.6D, where the processing module generates an operation code field toindicate the undo write request operation (e.g., an operation code valueof 24 hex) and generates a request/response value of zero for arequest/response field (e.g., indicating a request message) when thethreshold number of the one or more write commit responses have not beenreceived. The method continues at step 136 of FIG. 6D where theprocessing module determines a request number value for a request numberfield.

The method continues at step 388 where the processing module generates apayload of the request DSN frame by generating one or more slice namefields and one or more slice revision number fields. A slice name fieldincludes a slice name corresponding to a write commit response. A slicerevision numbering field includes a slice revision number correspondingto an associated slice name.

The method continues with step 358 of FIG. 17B where the processingmodule generates a payload length field of the protocol header toinclude a payload length that represents length of the one or more slicename fields and length of the one or more slice revision numberingfields. The method continues at step 392 where the processing modulepopulates the protocol header and the payload to produce the undo writerequest message.

The method continues at step 394 where the processing module outputs therequest DSN frame that includes the undo write request message in orderof the protocol header and one or more slice field pairs, wherein eachof the one or more slice field pairs includes, in order, a slice namefield of the one or more slice name fields and a slice revisionnumbering field of the one or more slice revision numbering fields,wherein the slice revision numbering field is associated with the slicename field.

Alternatively, or in addition to, the processing module generates aplurality of DSN frames regarding the conclusive write requestoperation, wherein the plurality of DSN frames includes the request DSNframe. Alternatively, or in addition to, the processing module updates aslice status table to indicate that slice names of the payload of theundo write request message are now not associated with a write-lockstatus since they are now an undo status and hence a previous writerequest operational function has concluded (e.g., a write transactionhas expired).

FIG. 20A is a diagram illustrating an example of a DSN frame for an undowrite response, which is one of the conclusive write responseoperations. The frame 396 includes a protocol header 112, which includesone or more of a protocol class field 116, a protocol class versionfield 118, an operation code field 120, a request/response field 122, arequest number field 124, and a payload length field 126. For example,the operation code field 120 includes an operation code value of 24 hex,the request/response field 122 includes a value of one, the requestnumber field 124 includes a request number extracted from an associatedundo write request message, and the payload length field 126 includes avalue of zero when the response DSN frame is associated with the undowrite response operational function.

In an operational example, the undo write response message 396 isgenerated and outputted in response to receiving and processing anassociated undo write request message when all encoded data slicescorresponding to the undo write request message are successfully undone(e.g., each encoded data slice that corresponds to a revision number ofthe associated undo write request message is deleted).

FIG. 20B is a flowchart illustrating an example of generating an undowrite response DSN frame, which includes similar steps to FIGS. 6D and14B. The method begins at step 398 where a processing module generatesfields of a protocol header to include values of the fields of theprotocol header. Step 398 includes steps 128-130 of FIG. 6D where theprocessing module generates a protocol class value for a protocol classfield and generates a protocol class version value for a protocol classversion field. Such generation of the fields of the protocol headerincludes generating the protocol class field to indicate a protocolclass for the conclusive write response operation (e.g., the undo writeresponse operation) and generating the protocol class version field toindicate a protocol class version for the conclusive write responseoperation.

The method continues at step 400, which includes steps 132-134 of FIG.6D, where the processing module generates an operation code field toindicate the conclusive write response operation (e.g., the undo writeresponse operation associated with an operation code value of 24 hex)and generates a request/response value of one for a request/responsefield (e.g., indicating a response message). The generating of theoperation code field includes creating the undo write response operationor extracting an operational code from a corresponding conclusive writerequest message (e.g., an undo write request message). The methodcontinues with step 136 of FIG. 6D, where the processing moduledetermines a request number value associated with a conclusive writerequest operation for a request number field (e.g., the processingmodule determines the request number by extracting a request number froman associated undo write request message).

The method continues with step 308 of FIG. 14B where the processingmodule generates a payload length field of the protocol header toinclude a predetermined payload length value (e.g., zero for theconclusive write response message). The method continues at step 406where the processing module populates the protocol header to produce theundo write response message. The method continues at step 408 where theprocessing module outputs in order, the protocol class field, theprotocol class version field, the operation code field, therequest/response field, the request number field, and the payload lengthfield as the response DSN frame of the undo write response message.Alternatively, or in addition to, the processing module may delete oneor more encoded data slices associated with one or more slice names andcorresponding one or more revision numbers of the associated undo writerequest message when the one or more encoded data slices are notassociated with a locked status of another open transaction notassociated with a current transaction of the conclusive write responseoperation.

FIG. 21A is a diagram illustrating an example of a check request DSNframe that includes a protocol header 112 and a payload 412. Theprotocol header 112 includes one or more of a protocol class field 116,a protocol class version field 118, an operation code field 120, arequest/response field 122, a request number field 124, and a payloadlength field 126. For example, the operation code field 120 includes anoperation code value of 30 hex and the request/response field 122includes a value of zero when the request DSN frame is associated withthe check request operational function.

The payload 412 includes a transaction number field 158 that includes atransaction value and slice name fields 1-n, each of which includes aslice name associated with the transaction value. A slice name isassociated with an encoded data slice, which is being checked forexistence (e.g., stored in a dispersed storage unit) per the checkstatus request. For example, the payload 412 includes a transactionnumber 158 and three 48 bytes slice name fields that includes slice name1, slice name 2, and slice name 3 when it is desired to check encodeddata slices associated with slice names 1-3. The method to generate thecheck request message 410 is described in greater detail with referenceto FIG. 21B.

FIG. 21B is a flowchart illustrating an example of generating a checkrequest DSN frame to support a check request operation, which includessimilar steps to FIGS. 6D and 7B. The method begins at step 414 where aprocessing module generates fields of a protocol header to includevalues of the fields of the protocol header. Step 414 includes steps128-130 of FIG. 6D where the processing module generates a protocolclass value for a protocol class field and generates a protocol classversion value for a protocol class version field. The generation of thefields of the protocol header includes generating the protocol classfield to indicate a protocol class for the check request operation andgenerating the protocol class version field to indicate a protocol classversion for the check request operation.

The method continues at step 416, which includes steps 132-134 of FIG.6D, where the processing module generates an operation code field toindicate a check request operation (e.g., an operation code value of 30hex) and generates a request/response value of zero for arequest/response field. The method continues at step 136 of FIG. 6Dwhere the processing module determines a request number value for arequest number field and continues at step 420 where the processingmodule generates a payload section of the request DSN frame regardingthe check request operation by generating one or more slice name fieldsof the payload section to include one or more slice names correspondingto one or more encoded data slices. The processing module may generatethe one or more slice names based on information received in a rebuildermessage, a previous check request, a list, a predetermination, a checkcommand, an error message, and a table lookup. For example, theprocessing module generates 1,000 slice names based on receiving arebuilder message that includes the 1,000 slice names to check if acorresponding plurality of encoded data slices associated with the 1,000slice names are stored on a dispersed storage unit.

The method continues with step 168 of FIG. 7B where the processingmodule generates a payload length field of the protocol header toinclude a payload length that represents a length of the payloadsection. The method continues with step 170 of FIG. 7B where theprocessing module generates a transaction number field of the payloadsection to include a transaction number value corresponding to the checkrequest operation.

The method continues at step 426 where the processing module populatesthe protocol header and the payload to produce the check requestmessage. The method continues at step 428 where the processing moduleoutputs the request DSN frame in order of the protocol header, thetransaction number field, and the one or more slice name fields.Alternatively, or in addition to, the processing module generates aplurality of DSN frames regarding the check request operation, whereinthe plurality of DSN frames includes the request DSN frame. In addition,the processing module may update a slice status table to indicate thatthe one or more slice names are associated with a read-lock status toprevent any further modifications of associated encoded data slicesuntil steps associated with the check request operation are completed(e.g., encoded data slices are checked in response to the check requestmessage).

FIG. 22A is a diagram illustrating an example of a check response DSNframe 430 that includes a protocol header 112 and a payload 432. Theprotocol header 112 includes one or more of a protocol class field 116,a protocol class version field 118, an operation code field 120, arequest/response field 122, a request number field 124, and a payloadlength field 126. For example, the operation code field 120 includes anoperation code value of 30 hex and the request/response field 122includes a value of one when the response DSN frame is associated withthe check response operational function.

The payload 432 includes one or more slice information sections 1-n thatcorrespond to one or more slice names 1-n of an associated check requestoperational function (e.g., one or more slice names 1-n extracted from acheck request DSN frame). Each slice information section includes aslice revision count field 434, one or more slice revision numberingfields 1-r, and one or more slice length fields 1-r, where r representsa slice revision count value of the slice revision count field 434. Theslice revision count value indicates a number of visible revisions of anassociated slice name included in the slice information section. Forexample, the slice revision count field is four bytes in length andincludes a slice revision count value of 7 when 7 encoded data slices of7 revisions are visible and associated with the corresponding slicename. As another example, the slice revision count value is set to zerowhen there is no encoded data associated with the corresponding slicename (e.g., the slice may have been deleted).

Each slice revision numbering field 1-r includes a revision number ofthe associated slice name. For example, a slice revision numbering fieldis eight bytes in length and includes a revision number that is greaterthan other revision numbers of the slice name when an encoded data sliceassociated with the revision number is a latest encoded data slice ofthe one or more encoded data slices associated with the slice name. Eachslice length field 1-r, for each of the revisions of the slice name,includes a length of a corresponding encoded data slice. For example, aslice length field value is set to 2,048 as a number of bytes of thecorresponding encoded data slice. As another example, the slice lengthfield value is set to zero when an encoded data slice of the revision ofthe corresponding slice name does not exist (e.g., the slice wasdeleted).

FIG. 22B is a flowchart illustrating an example of generating a checkresponse frame to support a check response operation, which includessimilar steps to FIG. 6D. The method begins at step 436 where aprocessing module generates fields of a protocol header to includevalues of the fields of the protocol header. Step 436 includes steps128-130 of FIG. 6D where the processing module generates a protocolclass value for a protocol class field and generates a protocol classversion value for a protocol class version field. The generation of thefields of the protocol header includes generating the protocol classfield to indicate a protocol class for the check response operation andgenerating the protocol class version field to indicate a protocol classversion for the check response operation.

The method continues at step 438, which includes steps 132-134 of FIG.6D, where the processing module generates an operation code field toindicate a check response operation (e.g., an operation code value of 30hex) and generates a request/response value of one for arequest/response field. The method continues with step 136 of FIG. 6Dwhere the processing module determines a request number value for arequest number field. The method continues at step 442 where theprocessing module generates a payload of the response DSN frameregarding one or more slice names of the check response operation toinclude one or more slice information sections. The generating of aslice information section includes generating a slice revision countfield to indicate a number of revisions of the slice name and generatinga slice revision number field to indicate a number of revisions of theslice name. Note that the slice revision count field may be set to zerowhen there are no revisions of the slice name (e.g., a deleted encodeddata slice).

The method continues at step 444 where the processing module generates aslice length field for each of the revisions of the slice name. Themethod continues at step 446 where the processing module generates apayload length field of the protocol header to include a payload lengththat represents a length of the slice information sections. The methodcontinues at step 448 where the processing module populates the protocolheader and the payload to produce the check response message.

The method continues at step 450 where the processing module outputs theresponse DSN frame in order of the protocol header, and the one or moreslice information sections, and, within each of the one or more sliceinformation sections, in an order of the slice revision count field, andfor each of the revisions of the slice name, the slice revisionnumbering field and the slice length field. In addition, the processingmodule may establish an error condition based on one or more of the oneor more slice names being associated with a locked encoded data slicestate, a transaction number error (e.g., a slice name is locked by asecond transaction number different from any transaction numberassociated with a corresponding read request message), the one or moreslice names are associated with one or more encoded data slices that arenot locally stored (e.g., a wrong DSN address), and a check requestmessage is not authorized (e.g., a requester is not authorized to accesssuch a portion of a DSN). The processing module discards the responseDSN frame when the error condition is established.

FIG. 23A is a diagram illustrating an example of a list range requestDSN frame 452 that includes a protocol header 112 and a payload 454. Theprotocol header 112 includes one or more of a protocol class field 116,a protocol class version field 118, an operation code field 120, arequest/response field 122, a request number field 124, and a payloadlength field 126. For example, the operation code field 120 includes anoperation code value of 60 hex and the request/response field 122includes a value of zero when the request DSN frame is associated withthe list range request operational function (e.g., retrieve a list ofencoded data slices (or slices names) stored by a DS unit within therange of slices names in the list request).

The payload 454 includes a start slice name range field 456 thatincludes a start slice name, an end slice name range field 458 thatincludes an end slice name, and a maximum response count field 460 thatincludes a maximum response count. The start slice name range field 456specifies a slice name to start an overall list range requestoperational function. The end slice name range field 458 specifies aslice name to end the overall list range request operational function.The maximum response count field 460 specifies a maximum number of slicenames to list in a subsequent list range response message.

FIG. 23B is a flowchart illustrating an example of generating a listrange request DSN frame to support a list range request operation, whichincludes similar steps to FIG. 6D. The method begins at step 462 where aprocessing module generates fields of a protocol header to includevalues of the fields of the protocol header. Step 462 includes steps128-130 of FIG. 6D where the processing module generates a protocolclass value for a protocol class field and generates a protocol classversion value for a protocol class version field. The generation of thefields of the protocol header includes generating the protocol classfield to indicate a protocol class for the list range request operationand generating the protocol class version field to indicate a protocolclass version for the list range request operation.

The method continues at step 464, which includes steps 132-134 of FIG.6D, where the processing module generates an operation code field toindicate the list range request operation (e.g., an operation code valueof 60 hex) and generates a request/response value of zero for arequest/response field. The method continues at step 136 of FIG. 6Dwhere the processing module determines a request number value for arequest number field.

The method continues at step 468 where the processing module generates apayload section of the request DSN frame regarding the list rangerequest operation by generating a start slice name field of the payloadsection to include a start slice name of a slice name range. Thegenerating of the start slice name includes one of establishing thestart slice name as a first slice name in a spectrum of slice names(e.g., all possible slice names in the system or a portion thereof),establishing the start slice name as an intermediate slice name in thespectrum of slice names, and determining the start slice name based on aresponse to a previous list range request operation. The spectrum ofslice names includes one or more ranges of slice names. For example, theprocessing module generates the start slice name as a first slice nameof a first slice name range of a first spectrum of slice names when alist range request operational function is initiated. As anotherexample, the processing module generates the start slice name as anintermediate slice name of a fifth slice name range of the firstspectrum of slice names when the list range request operational functionhas been initiated but is not finished. As yet another example, theprocessing module determines the start slice name as a last slice nameextracted from a response from a previous list range request operation.

At step 468 the processing module generates an end slice name field ofthe payload section to include an end slice name of the slice namerange. The generating of the end slice name includes one of establishingthe end slice name as a last slice name in the spectrum of slice names,establishing the end slice name as a second intermediate slice name inthe spectrum of slice names, and determining the end slice name based onthe response to the previous list range request operation. For example,the processing module generates the end slice name as a last slice nameof a final slice name range of a first spectrum of slice names when thelist range request operational function is completed. As anotherexample, the processing module generates the end slice name as a secondintermediate slice name of the fifth slice name range of the firstspectrum of slice names when the list range request operational functionhas been initiated but is not finished. As yet another example, theprocessing module determines the end slice name as the last slice nameextracted from the response from the previous list range requestoperation incremented by an increment value (e.g., a maximum responsecount).

The method continues at step 470 where the processing module generates amaximum response count field of the payload section to include a maximumslice name response count. The generating of the maximum response countincludes at least one of determining the maximum response count based ona number of slice names in the spectrum of slice names, determining themaximum response count based on a DSN performance indicator (e.g.,indicating when a very large response message is undesirable), anddetermining the maximum response count based on the response to theprevious list range request operation. For example, processing modulegenerates the maximum slice name response count based on a number ofslice names of the previous list range request operation.

The method continues at step 472 where the processing module determinesa length of the start slice name field, a length of the end slice namefield, a length of the maximum response count field, and generates apayload length for a payload length field based on the length of thestart slice name field, the length of the end slice name field, and thelength of the maximum response count field. The method continues at step474 where the processing module populates the payload length field ofthe protocol header to include the payload length and populates thepayload section with the start slice name field, the end slice namefield, and the maximum response count field.

The method continues at step 476 where the processing module outputs therequest DSN frame in order of the protocol header, the start slice namefield, the end slice name field, and the maximum response count field tosend a list range request message. Alternatively, or in addition to, theprocessing module generates a plurality of DSN frames regarding the listrange request operation, wherein the plurality of DSN frames includesthe request DSN frame.

FIG. 24A is a diagram illustrating an example of a list range responseDSN frame 478 that includes a protocol header 112 and a payload 480. Theprotocol header 112 includes one or more of a protocol class field 116,a protocol class version field 118, an operation code field 120, arequest/response field 122, a request number field 124, and a payloadlength field 126. For example, the operation code field 120 includes anoperation code value of 60 hex and the request/response field 122includes a value of one when the response DSN frame is associated withthe list range response operational function.

The payload 480 includes a last slice name field 482, which includes alast slice name of one or more slice names. The last slice name isassociated with a last slice information section and/or with one or moreslice information sections 1-n that correspond to one or more slicenames 1-n of the list range response operational function. Each sliceinformation section 1-n includes a slice name field that includes aslice name, a slice revision count field 484, one or more slice revisionnumbering fields 1-r, and one or more slice length fields 1-r, where rrepresents a slice revision count value of the slice revision countfield 484. The slice revision count value indicates a number of visiblerevisions of an associated slice name included in the slice informationsection. For example, the slice revision count field is four bytes inlength and includes a slice revision count value of 4 when 4 encodeddata slices of 4 revisions are visible associated with the slice name.As another example, the slice revision count value is set to zero whenthere is no encoded data slice that is associated with the slice name(e.g., the encoded data slice may have been deleted).

Each slice revision numbering field 1-r includes a revision number ofthe slice name. For example, a slice revision numbering field is eightbytes in length and includes a revision number that is greater thanother revision numbers of the slice name when an encoded data sliceassociated with the revision number is a latest encoded data sliceassociated with the slice name. Each slice length field 1-r, for each ofthe revisions of the slice name, includes a length of a correspondingencoded data slice. For example, a slice length field value is set to2,048 as a number of bytes of the corresponding encoded data slice. Asanother example, the slice length field value is set to zero when anencoded data slice of the revision of the corresponding slice name doesnot exist (e.g., the slice was deleted).

FIG. 24B is a flowchart illustrating an example of generating a listrange response (DSN frame to support a list range response operation).The method begins at step 486 where a processing module generates fieldsof a protocol header to include values of the fields of the protocolheader. Step 486 includes steps 128-130 of FIG. 6D where the processingmodule generates a protocol class value for a protocol class field andgenerates a protocol class version value for a protocol class versionfield. The generation of the fields of the protocol header includesgenerating the protocol class field to indicate a protocol class for thelist range response operation and generating the protocol class versionfield to indicate a protocol class version for the list range responseoperation.

The method continues at step 488, which includes steps 132-134 of FIG.6D, where the processing module generates an operation code field toindicate the list range response operation (e.g., an operation codevalue of 60 hex) and generates a request/response value of one for arequest/response field. The method continues with step 136 of FIG. 6Dwhere the processing module determines a request number value for arequest number field.

The method continues at step 492 where the processing module determinesone or more slice information sections by at least one of determining anumber of slice names of one or more slice names in a slice name rangeassociated with a list range request, determining a number of slicenames based on a DSN performance indicator, and determining a number ofslice names associated with the list range response operation.

The method continues at step 494 where the processing module generates apayload of the response DSN frame regarding the one or more slice namesof the list range response operation to include generating a last slicename field to include a last slice name and generating the one or moreslice information sections, wherein a slice information section of theone or more slice information sections includes generating a slice namefield to include a slice name of the one or more slice names, generatinga slice revision count field to indicate a number of revisions of theslice name, generating a slice revision numbering field for each of therevisions of the slice name to include a revision number to produce oneor more slice revision numbering fields, and generating a slice lengthfield for each of the revisions of the slice name to include a length ofa corresponding encoded data slice.

The method continues at step 496 where the processing module determinesthe last slice name as a slice name associated with a last sliceinformation section of the one or more slice information sections. Notethat the last slice name indicates a starting point for a subsequentlist request operational function and may include a last slice name of aslice name range associated with a dispersed storage unit when there areno more slice names to be listed. At step 496 the processing modulegenerates a payload length field of the protocol header to include apayload length that represents a length of the slice name field and thelength of the one or more slice information sections. The methodcontinues at step 498 where the processing module populates the protocolheader and the payload to produce the list range response message.

The method continues at step 500 where the processing module outputs theresponse DSN frame in order of the protocol header, the last slice namefield, and the one or more slice information sections and, within theslice information section, in an order of the slice revision countfield, and, for each of the revisions of the slice name, the slicerevision numbering field and the slice length field. In addition, theprocessing module may establish an error condition based on one or moreof the one or more slice names being associated with a locked encodeddata slice state, the one or more slice names are associated with one ormore encoded data slices that are not locally stored (e.g., a wrong DSNaddress), and a list range request message is not authorized (e.g., arequester is not authorized to access such a portion of a DSN). Theprocessing module discards the response DSN frame when the errorcondition is established.

FIG. 25A is a diagram illustrating an example of a list digest requestDSN frame 502 that includes a protocol header 112 and a payload 504. Theprotocol header 112 includes one or more of a protocol class field 116,a protocol class version field 118, an operation code field 120, arequest/response field 122, a request number field 124, and a payloadlength field 126. For example, the operation code field 120 includes anoperation code value of 61 hex and the request/response field 122includes a value of zero when the request DSN frame is associated withthe list digest request operational function.

The payload 504 includes a start slice name range field 506 thatincludes a start slice name, an end slice name range field 508 thatincludes an end slice name, and a maximum response count field 510 thatincludes a maximum response count. The start slice name range field 506specifies a slice name to start an overall list digest requestoperational function. The end slice name range field 508 specifies aslice name to end the overall list digest request operational function.The maximum response count field 510 specifies a maximum number of slicenames to include in a digest of the list digest request operationalfunction.

FIG. 25B is a flowchart illustrating an example of generating a listdigest request DSN frame to support a list digest request operation. Themethod begins at step 512 where a processing module generates fields ofa protocol header to include values of the fields of the protocolheader. Step 512 includes steps 128-130 of FIG. 6D where the processingmodule generates a protocol class value for a protocol class field andgenerates a protocol class version value for a protocol class versionfield. The generation of the fields of the protocol header includesgenerating the protocol class field to indicate a protocol class for thelist digest request operation and generating the protocol class versionfield to indicate a protocol class version for the list digest requestoperation.

The method continues at step 514, which includes steps 132-134 of FIG.6D, where the processing module generates an operation code field toindicate the list digest request operation (e.g., an operation codevalue of 61 hex) and generates a request/response value of zero for arequest/response field. The method continues at step 136 of FIG. 6Dwhere the processing module determines a request number value for arequest number field.

The method continues at step 518 where the processing module generates apayload section of the request DSN frame regarding the list digestrequest operation by generating a start slice name field of the payloadsection to include a start slice name of a slice name range. Thegenerating of the start slice name includes one of establishing thestart slice name as a first slice name in a spectrum of slice names,establishing the start slice name as an intermediate slice name in thespectrum of slice names, and determining the start slice name based on aresponse to a previous list digest request operation.

At step 518 the processing module generates an end slice name field ofthe payload section to include an end slice name of the slice namerange. The generating of the end slice name includes one of establishingthe end slice name as a last slice name in the spectrum of slice names,establishing the end slice name as a second intermediate slice name inthe spectrum of slice names, and determining the end slice name based onthe response to the previous list digest request operation. For example,the processing module generates the end slice name as a last slice nameof a final slice name range of a first spectrum of slice names when thelist digest request operational function is completing. As anotherexample, the processing module generates the end slice name as a secondintermediate slice name of the fifth slice name range of the firstspectrum of slice names when the list digest request operationalfunction has been initiated but is not finished. As yet another example,the processing module determines the end slice name as the last slicename extracted from the response from the previous list digest requestoperation incremented by an increment value (e.g., a maximum responsecount).

The method continues at step 520 where the processing module generates amaximum response count field of the payload section to include a maximumslice name response count. The generating of the maximum response countincludes at least one of determining the maximum response count based ona number of slice names in the spectrum of slice names, determining themaximum response count based on a DSN performance indicator (e.g.,indicating when a very large response message is undesirable), anddetermining the maximum response count based on the response to theprevious list digest request operation. For example, the processingmodule generates the maximum slice name response count based on a numberof slice names of the previous list digest request operation.

The method continues at step 472 of FIG. 23B where the processing modulegenerates a payload length for a payload length field. The methodcontinues at step 524 where the processing module populates the payloadlength field of the protocol header to include the payload length andpopulates the payload section with the start slice name field, the endslice name field, and the maximum response count field.

The method continues at step 526 where the processing module outputs therequest DSN frame in order of the protocol header, the start slice namefield, the end slice name field, and the maximum response count field tosend a list digest request message. Alternatively, or in addition to,the processing module generates a plurality of DSN frames regarding thelist digest request operation, wherein the plurality of DSN framesincludes the request DSN frame.

FIG. 26A is a diagram illustrating an example of a list digest responseDSN frame 528 that includes a protocol header 112 and a payload 530. Theprotocol header 112 includes one or more of a protocol class field 116,a protocol class version field 118, an operation code field 120, arequest/response field 122, a request number field 124, and a payloadlength field 126. For example, the operation code field 120 includes anoperation code value of 61 hex and the request/response field 122includes a value of one when the response DSN frame is associated withthe list digest response operational function.

The payload 530 includes a digest length field 532 including a length ofa digest, a digest field 534 that includes the digest, wherein thedigest includes a representation of slice names in a slice name range, alast slice name field 536 that includes a last slice name of the slicename range, and a slice count field 538 that includes an indication of anumber of slice names of the list digest response operation. Forexample, the digest length field 532 is two bytes in length and includesa length of 64 bytes when the digest is 512 bits.

Such a slice count field indicates a number of slice names of the listdigest response operation that is less than or equal to a value of amaximum response count in a corresponding list digest request message.For example, the slice count field 538 is four bytes in length andincludes an indication of 1,000,000 slice names of the list digestresponse operation when there is at least one visible (e.g.,retrievable) revision of an encoded data slice associated with eachslice name of 1,000,000 slice names. As another example, the indicationof the number of slice names is zero when there are no visible encodeddata slices corresponding to slice names within the slice name range.

The representation of slice names in the slice name range includes ahashing function result. For example, the digest represents a hash overa slice name/revision list that includes one or more slice names of theslice name range and one or more corresponding revision numbers for eachslice name, wherein each slice name of the one more slice namescorresponds to at least one visible encoded data slice.

FIG. 26B is a flowchart illustrating an example of generating a listdigest response frame to support a list digest response operation. Themethod begins at step 540 where a processing module generates fields ofa protocol header to include values of the fields of the protocolheader. Step 540 includes steps 128-130 of FIG. 6D where the processingmodule generates a protocol class value for a protocol class field andgenerates a protocol class version value for a protocol class versionfield. The generation of the fields of the protocol header includesgenerating the protocol class field to indicate a protocol class for thelist digest response operation and generating the protocol class versionfield to indicate a protocol class version for the list digest responseoperation.

The method continues at step 542, which includes steps 132-134 of FIG.6D, where the processing module generates an operation code field toindicate the list digest response operation (e.g., an operation codevalue of 61 hex) and generates a request/response value of one for arequest/response field. The method continues with step 136 of FIG. 6Dwhere the processing module determines a request number value for arequest number field.

The method continues at step 546 where the processing module determinesa slice name range based on at least one of a start slice name of a listdigest request, an end slice name of the list digest request, a lastslice name of a list digest response, and a DSN performance indicator.For example, the processing module determines the slice name range fromthe start slice name of the list digest request to the end slice name ofthe list digest request. As another example, the processing moduledetermines the slice name range as half of the slice names from thestart slice name to the end slice name of the list digest request whenthe DSN performance indicator compares unfavorably to a performancethreshold (e.g., limited processing availability).

The method continues at step 548 where the processing module generates apayload of the response DSN frame regarding one or more slice names ofthe list digest response operation by generating a digest length fieldto include a length of a digest, wherein the digest includes arepresentation of slice names in the slice name range. The processingmodule generates a digest field to include the digest, which may be ahash function of at least a portion of a slice name/revision listassociated with at least some of a plurality of slices names within theslice name range. The slice name/revision list includes, for a slicename of the plurality of slices names, a slice name of the one or moreslice names, a slice revision count indicating a number of revisions ofthe slice name, one or more slice revision numbers for each of therevisions of the slice name, and one or more slice length indicatorscorresponding to each of the revisions of the slice name to include alength of a corresponding encoded data slice.

At step 548, the processing module generates a last slice name field toinclude a last slice name of the slice name range. The generation of thelast slice name includes one of selecting an end slice name of the slicename range and using a final slice name as indicated in a list digestrequest DSN frame. Note that the last slice name indicates a startingpoint for a subsequent list digest request operational function and mayinclude a last slice name of a slice name range associated with adispersed storage unit when there are no more slice names to be listed.The processing module generates a slice count field to indicate a numberof slice names of the list digest response operation. The generation ofthe number of slice names of the list digest response operation includesat least one of determining the number based on the plurality of slicesnames within the slice name range and determining the number based onvisible encoded data slices associated with at least some of theplurality of slice names.

The method continues at step 550 where the processing module generates apayload length field of the protocol header to include a payload lengththat represents a sum of a length of the digest length field, the digestfield, the last slice name field, and the slice count field. The methodcontinues at step 552 where the processing module populates the payloadsection with digest length field, the digest field, the last slice namefield, and the slice count field to produce the list digest responsemessage.

The method continues at step 554 where the processing module outputs theresponse DSN frame in order of the protocol header, the digest lengthfield, the digest field, the last slice name field, and the slice countfield to send the list digest response message. Alternatively, or inaddition to, the processing module establishes an error condition basedon one or more of the one or more slice names being associated with alocked encoded data slice state, the one or more slice names areassociated with one or more encoded data slices that are not locallystored, and a list digest message is not authorized. The processingmodule discards the DSN frame when the error condition is established.

FIGS. 27A-C is a schematic block diagram of an embodiment of a dispersedstorage network (DSN) that includes the dispersed storage (DS)processing unit 16 of FIG. 1, the network 24 of FIG. 1, and the DSNmemory 22 of FIG. 1. The DSN memory 22 includes a set of DS units 1-5.Each DS unit may be implemented utilizing the DS unit 36 of FIG. 1.Hereafter, each DS unit may be referred to interchangeably as a storageunit and the set of DS units may be referred to interchangeably as a setof storage units.

The DSN functions to store data in the DSN memory 22 utilizing a seriesof protocol commands. The protocol commands includes one or more of awrite slice request transaction, a write slice response, a rollbacktransaction request, a rollback transaction response, a commit requesttransaction, a commit response transaction acknowledgment, a finalizeslice request, a finalize slice response acknowledgment, an undo slicerequest, and an undo slice response acknowledgment.

Each DS unit may store one or more revisions of encoded data slices,where a data segment with a previous revision level is dispersed storageerror encoded to produce a set of previous revision level encoded dataslices for storage in the set of DS units. For example, the DSprocessing unit 16 previously encodes the data segment of the previousrevision level to produce a set of previous revision level (e.g., level2) encoded data slices 1R2, 2R2, 3R2, 4R2, and 5R2 for previous storagein a set of DS units 1-5. Subsequent to successful storage of the set ofprevious revision level encoded data slices, the set of previousrevision level encoded data slices are available for accessing.

FIG. 27A illustrates initial steps of an example of the storing of thedata where the DS processing unit 16 dispersed storage error encodes acurrent revision level of a data segment (e.g., revision level 3) toproduce a set of current revision level encoded data slices and sends,via the network 24, a set of write commands to the storage units of theDSN regarding storage of the set of current revision level encoded dataslices. For example, the DS processing unit 16 generates the set ofwrite commands to include a set of current revision level encoded dataslices 1R3, 2R3, 3R3, 4R3, and 5R3.

A DS unit receiving a corresponding write command of the set of writecommands stores a current revision level encoded data slice of the setof current revision level encoded data slices but does not make thestored current revision level encoded data slice available foraccessing. Having stored the current revision level encoded data slice,the DS unit sends, via the network 24, a write acknowledgment inresponse to the corresponding recommend. For example, DS unit 1 storesthe current revision level encoded data slice 1R3 and sends a writeacknowledgment for the received and stored current revision levelencoded data slice 1R3. As another example, DS unit 5 stores the currentrevision level encoded data slice 5R3 but fails to send a writeacknowledgment for the received and stored current revision levelencoded data slice 5R3 due to a failure (e.g., processing error, networkconnectivity issue, etc.).

The DS processing unit 16 receives write acknowledgments from the DSunits. For example, the DS processing unit 16 receives, via the network24, a write acknowledgement in response to a write command of the set ofwrite commands from one of the storage units indicating that the one ofthe storage units successfully stored, but has not made available foraccessing, a current revision level encoded data slice of the set ofcurrent revision level encoded data slices. For instance, the DSprocessing unit 16 receives the write acknowledgment for the receivedand stored current revision level encoded data slice 1R3, and forreceived and stored current revision level encoded data slices 2R3, 3R3,and 4R3, but does not receive the write acknowledgment from the receivedand stored current revision level encoded data slice 5R3.

Having received the write acknowledgments from the DS units, the DSprocessing unit 16 determines whether a write threshold number of writeacknowledgements have been received within a given period indicatingthat a write threshold number of current revision level encoded dataslices of the set of current revision level encoded data slices havebeen successfully stored, but are not yet available for accessing. Forexample, the DS processing unit 16 indicates that the write thresholdnumber of write acknowledgments have been received when receiving thewrite acknowledgments for received and stored current revision levelencoded data slices 1R3, 2R3, 3R3, and 4R3 when the write thresholdnumber is 4. When the write threshold number of write acknowledgementshave not been received within the given period, the DS processing unit16 issues, via the network 24, a set of rollback commands to the storageunits.

FIG. 27B illustrates further steps of the example of the storing of thedata where, when the write threshold number of write acknowledgementshave been received within the given period, the DS processing unit 16issues, via the network 24, a set of commit commands to the storageunits regarding making the successfully stored encoded data slicesavailable for accessing. For example, the DS processing unit 16 issues aset of commit commands for the current revision level encoded dataslices 1R3 through 5R3.

Each DS unit receiving a corresponding commit command makes acorresponding current revision level encoded data slice available foraccessing. For example, DS unit 2 makes the current revision levelencoded data slice 2R3 available for accessing when receiving the commitcommand corresponding to the current revision level encoded data slice2R3. Having made the corresponding current revision level encoded dataslice available for accessing, each DS unit issues, via the network 24,a commit acknowledgment to the DS processing unit 16 in response to thecorresponding commit command.

The DS processing unit 16 receives commit acknowledgments from the DSunits. For example, the DS processing unit 16 receives, via the network24, a commit acknowledgement in response to a commit command of the setof commit commands from the one of the storage units indicating that theone of the storage units has made the current revision level encodeddata slice available for accessing. For instance, the DS processing unit16 receives commit acknowledgments for the current revision levelencoded data slices 1R3, 2R3, 3R3, and 4R3, but not for the currentrevision level encoded data slice 5R3 when the failure occurs associatedwith DS unit 5.

Subsequent to issuing the set of commit commands, the DS processing unit16 determines whether to issue a set of finalize commands, where afinalize command of the set of finalize commands instructs a storageunit of the storage units regarding storage of a corresponding currentrevision level encoded data slice of the set of current revision levelencoded data slices and storage of a previous revision level encodeddata slice of a set of previous revision level encoded data slices. TheDS processing unit 16 may initiate the determining of whether to issuethe set of finalize commands by one of receiving a request for dispersedstorage error encoded storage of a data segment having a more recentrevision level than the current revision level and receiving a requestto make the determination.

The determining whether to issue the set of finalize commands may bebased on one or more of the write threshold number, a predeterminednumber, and a number of received commit acknowledgments. As a specificexample, DS processing unit 16 does not issue the set of finalizecommands when a number of received commit acknowledgements is below thepredetermined number. For example, the DS processing unit 16 determinesnot to issue the set of finalize commands when receiving 4 commitacknowledgments and the predetermined number is 5.

As another specific example, the DS processing unit 16 determineswhether a write threshold number of commit acknowledgments have beenreceived from the storage units. When the write threshold number ofcommit acknowledgments have been received from the storage units, the DSprocessing unit 16 issues, via the network 24, the set of finalizecommands to the set of DS units. When the write threshold number ofcommit acknowledgments have not been received from the storage units,the DS processing unit 16 issues a set of undo commands to the storageunits. As yet another specific example, the DS processing unit 16determines not to issue the set of finalize commands when receiving acommand to not issue the set of finalize commands.

FIG. 27C illustrates still further steps of the storing of the datawhere the DS processing unit 16 receives a commit acknowledgment forcurrent level encoded data slice 5R3 (e.g., upon resolution of thefailure associated with DS unit 5). The DS processing unit 16 determinesthat the predetermined number of commit acknowledgments have beenreceived from the storage units, where the predetermined number isgreater than the write threshold (e.g., predetermined number=5, writethreshold number=4). Having determined that the predetermined number ofcommit acknowledgments have been received from the storage units, the DSprocessing unit 16 issues, via the network 24, the set of finalizecommands to the set of DS units. For example, the DS processing unit 16issues the set of finalize commands for the current revision levelencoded data slices 1R3 through 5R3.

The DS processing unit 16 generates the set of finalize commands toinclude instructions to the DS units with regards to storage and/ordeletion of encoded data slices of the current revision level encodeddata slices and the previous revision level encoded data slices. As aspecific example, a finalize command of the set of finalize commandsincludes an instruction to maintain storage of the current revisionlevel encoded data slice and to delete the previous revision levelencoded data slice. For instance, DS unit 4 maintains current revisionlevel encoded data slice 4R3 and deletes previous revision level encodeddata slice 4R2. As another specific example, the finalize commandincludes an instruction to maintain storage of both of the currentrevision level encoded data slice and the previous revision levelencoded data slice. As yet another example, the finalize commandincludes an instruction to delete the current revision level encodeddata slice and to maintain storage of the previous revision levelencoded data slice.

FIG. 27D is a flowchart illustrating an example of storing data. Inparticular, a method is presented for use in conjunction with one ormore functions and features described in conjunction with FIGS. 1-5,27A-C, and also FIG. 27D. The method continues at step 600 and where aprocessing module of a computing device of a dispersed storage network(DSN) sends a set of write commands to storage units of the DSNregarding storage of a set of current revision level encoded dataslices, where a current revision level of a data segment is dispersedstorage error encoded to produce the set of current revision levelencoded data slices.

The method continues at step 602 where the processing module receives awrite acknowledgement in response to a write command of the set of writecommands from one of the storage units indicating that the one of thestorage units successfully stored, but has not made available foraccessing, a current revision level encoded data slice of the set ofcurrent revision level encoded data slices. The method continues at step604 where the processing module determines whether a write thresholdnumber of write acknowledgements have been received within a givenperiod indicating that a write threshold number of current revisionlevel encoded data slices of the set of current revision level encodeddata slices have been successfully stored, but are not yet available foraccessing.

When the write threshold number of write acknowledgements have beenreceived within the given period, the method continues at step 606 wherethe processing module issues a set of commit commands to the storageunits regarding making the successfully stored encoded data slicesavailable for accessing. Alternatively, when the write threshold numberof write acknowledgements have not been received within the givenperiod, the processing module issues a set of rollback commands to thestorage units.

The method continues at step 608 where the processing module receives acommit acknowledgement in response to a commit command of the set ofcommit commands from the one of the storage units indicating that theone of the storage units has made the current revision level encodeddata slice available for accessing. The method continues at step 610where, subsequent to issuing the set of commit commands, the processingmodule determines whether to issue a set of finalize commands.

A finalize command of the set of finalize commands instructs a storageunit of the storage units regarding storage of a corresponding currentrevision level encoded data slice of the set of current revision levelencoded data slices and storage of a previous revision level encodeddata slice of a set of previous revision level encoded data slices,where a data segment with the previous revision level is dispersedstorage error encoded to produce the set of previous revision levelencoded data slices. As a specific example, the processing modulereceives a command to not issue the set of finalize commands. Thefinalize command may include one of an instruction to maintain storageof the current revision level encoded data slice and to delete theprevious revision level encoded data slice, an instruction to maintainstorage of both of the current revision level encoded data slice and theprevious revision level encoded data slice, and an instruction to deletethe current revision level encoded data slice and to maintain storage ofthe previous revision level encoded data slice. The processing modulemay initiate the determining of whether to issue the set of finalizecommands by one of receiving a request for dispersed storage errorencoded storage of a data segment having a more recent revision levelthan the current revision level and receiving a request to make thedetermination.

The processing module may compare a number of received commitacknowledgments to a number to determine whether to issue the set offinalize commands. The number may include one of a decode thresholdnumber, a write threshold number, a predetermined number, and aninformation dispersal algorithm (IDA) width number. When utilizing thepredetermined number and a predetermined number of received commitacknowledgments has been received, the method branches to step 614. Whenutilizing the predetermined number and less than the predeterminednumber of commit acknowledgments has been received, the method branchesto step 616. When utilizing the write threshold number, the methodcontinues to step 612.

The method continues at step 612, where the processing module determineswhether the write threshold number of commit acknowledgments have beenreceived from the storage units. When the write threshold number ofcommit acknowledgments have been received from the storage units, theprocessing module issues the set of finalize commands. Alternatively,when the write threshold number of commit acknowledgments have not beenreceived from the storage units, the processing module issues a set ofundo commands to the storage units.

When utilizing the predetermined number and the predetermined number ofreceived commit acknowledgments has been received, the method continuesat step 614 where the processing module issues the set of finalizecommands when the predetermined number of commit acknowledgments havebeen received from the storage units, where the predetermined number isgreater than the write threshold number. When utilizing thepredetermined number and less than the predetermined number of commitacknowledgments has been received, the method continues at step 616where the processing module determines not to issue the set of finalizecommands when the number of received commit acknowledgements is belowthe predetermined number.

The method described above in conjunction with a processing module canalternatively be performed by other modules of a dispersed storagenetwork or by other devices. In addition, at least one memory sectionthat stores operational instructions can, when executed by one or moreprocessing modules of one or more computing devices of a dispersedstorage network (DSN), cause the one or more computing devices toperform any or all of the method steps described above.

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “operably coupled to”, “coupled to”, and/or “coupling” includesdirect coupling between items and/or indirect coupling between items viaan intervening item (e.g., an item includes, but is not limited to, acomponent, an element, a circuit, and/or a module) where, for indirectcoupling, the intervening item does not modify the information of asignal but may adjust its current level, voltage level, and/or powerlevel. As may further be used herein, inferred coupling (i.e., where oneelement is coupled to another element by inference) includes direct andindirect coupling between two items in the same manner as “coupled to”.As may even further be used herein, the term “operable to” or “operablycoupled to” indicates that an item includes one or more of powerconnections, input(s), output(s), etc., to perform, when activated, oneor more its corresponding functions and may further include inferredcoupling to one or more other items. As may still further be usedherein, the term “associated with”, includes direct and/or indirectcoupling of separate items and/or one item being embedded within anotheritem. As may be used herein, the term “compares favorably”, indicatesthat a comparison between two or more items, signals, etc., provides adesired relationship. For example, when the desired relationship is thatsignal 1 has a greater magnitude than signal 2, a favorable comparisonmay be achieved when the magnitude of signal 1 is greater than that ofsignal 2 or when the magnitude of signal 2 is less than that of signal1.

While the transistors in the above described figure(s) is/are shown asfield effect transistors (FETs), as one of ordinary skill in the artwill appreciate, the transistors may be implemented using any type oftransistor structure including, but not limited to, bipolar, metal oxidesemiconductor field effect transistors (MOSFET), N-well transistors,P-well transistors, enhancement mode, depletion mode, and zero voltagethreshold (VT) transistors.

The present invention has also been described above with the aid ofmethod steps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claimed invention.

The present invention has been described, at least in part, in terms ofone or more embodiments. An embodiment of the present invention is usedherein to illustrate the present invention, an aspect thereof, a featurethereof, a concept thereof, and/or an example thereof. A physicalembodiment of an apparatus, an article of manufacture, a machine, and/orof a process that embodies the present invention may include one or moreof the aspects, features, concepts, examples, etc., described withreference to one or more of the embodiments discussed herein.

The present invention has been described above with the aid offunctional building blocks illustrating the performance of certainsignificant functions. The boundaries of these functional buildingblocks have been arbitrarily defined for convenience of description.Alternate boundaries could be defined as long as the certain significantfunctions are appropriately performed. Similarly, flow diagram blocksmay also have been arbitrarily defined herein to illustrate certainsignificant functionality. To the extent used, the flow diagram blockboundaries and sequence could have been defined otherwise and stillperform the certain significant functionality. Such alternatedefinitions of both functional building blocks and flow diagram blocksand sequences are thus within the scope and spirit of the claimedinvention. One of average skill in the art will also recognize that thefunctional building blocks, and other illustrative blocks, modules andcomponents herein, can be implemented as illustrated or by discretecomponents, application specific integrated circuits, processorsexecuting appropriate software and the like or any combination thereof.

What is claimed is:
 1. A method for execution by one or more processingmodules of one or more computing devices of a dispersed storage network(DSN), the method comprises: sending a set of write commands to storageunits of the DSN regarding storage of a set of current revision levelencoded data slices, wherein a current revision level of a data segmentis dispersed storage error encoded to produce the set of currentrevision level encoded data slices; receiving a write acknowledgement inresponse to a write command of the set of write commands from one of thestorage units indicating that the one of the storage units successfullystored, but has not made available for accessing, a current revisionlevel encoded data slice of the set of current revision level encodeddata slices; determining whether a write threshold number of writeacknowledgements have been received within a given period indicatingthat a write threshold number of current revision level encoded dataslices of the set of current revision level encoded data slices havebeen successfully stored, but are not yet available for accessing; whenthe write threshold number of write acknowledgements have been receivedwithin the given period, issuing a set of commit commands to the storageunits regarding making successfully stored current revision levelencoded data slices available for accessing; and subsequent to issuingthe set of commit commands, determining whether to issue a set offinalize commands based on one of: receiving a request for dispersedstorage error encoded storage of a data segment having a more recentrevision level than the current revision level and receiving a requestto make the determination; wherein a finalize command of the set offinalize commands instructs a storage unit of the storage unitsregarding storage of a corresponding current revision level encoded dataslice of the set of current revision level encoded data slices andstorage of a previous revision level encoded data slice of a set ofprevious revision level encoded data slices, wherein the data segmentwith the previous revision level is dispersed storage error encoded toproduce the set of previous revision level encoded data slices.
 2. Themethod of claim 1 further comprises: receiving a commit acknowledgementin response to a commit command of the set of commit commands from theone of the storage units indicating that the one of the storage unitshas made the current revision level encoded data slice available foraccessing; issuing the set of finalize commands when a predeterminednumber of commit acknowledgments have been received from the storageunits, wherein the predetermined number is greater than the writethreshold number of current revision level encoded data slices; and notissuing the set of finalize commands when a number of received commitacknowledgements is below the predetermined number.
 3. The method ofclaim 1 further comprises: when the determining whether to issue the setof finalize commands is initiated: determining whether a write thresholdnumber of commit acknowledgments have been received from the storageunits; when the write threshold number of commit acknowledgments havebeen received from the storage units, issuing the set of finalizecommands; and when the write threshold number of commit acknowledgmentshave not been received from the storage units, issuing a set of undocommands to the storage units.
 4. The method of claim 1 furthercomprises: receiving a command to not issue the set of finalizecommands.
 5. The method of claim 1, wherein the finalize commandcomprises: an instruction to maintain storage of the current revisionlevel encoded data slice and to delete the previous revision levelencoded data slice.
 6. The method of claim 1, wherein the finalizecommand comprises: an instruction to maintain storage of both of thecurrent revision level encoded data slice and the previous revisionlevel encoded data slice.
 7. The method of claim 1, wherein the finalizecommand comprises: an instruction to delete the current revision levelencoded data slice and to maintain storage of the previous revisionlevel encoded data slice.
 8. The method of claim 1 further comprises:when the write threshold number of write acknowledgements have not beenreceived within the given period, issuing a set of rollback commands tothe storage units.
 9. A non-transitory computer readable storage mediumcomprises: at least one memory section that stores operationalinstructions that, when executed by one or more processing modules ofone or more computing devices of a dispersed storage network (DSN),causes the one or more computing devices to: send a set of writecommands to storage units of the DSN regarding storage of a set ofcurrent revision level encoded data slices, wherein a current revisionlevel of a data segment is dispersed storage error encoded to producethe set of current revision level encoded data slices; receive a writeacknowledgement in response to a write command of the set of writecommands from one of the storage units indicating that the one of thestorage units successfully stored, but has not made available foraccessing, a current revision level encoded data slice of the set ofcurrent revision level encoded data slices; determine whether a writethreshold number of write acknowledgements have been received within agiven period indicating that a write threshold number of currentrevision level encoded data slices of the set of current revision levelencoded data slices have been successfully stored, but are not yetavailable for accessing; when the write threshold number of writeacknowledgements have been received within the given period, issue a setof commit commands to the storage units regarding making successfullystored current revision level encoded data slices available foraccessing; and subsequent to issuing the set of commit commands,determine whether to issue a set of finalize commands based on one of:receiving a request for dispersed storage error encoded storage of adata segment having a more recent revision level than the currentrevision level and receiving a request to make the determination;wherein a finalize command of the set of finalize commands instructs astorage unit of the storage units regarding storage of a correspondingcurrent revision level encoded data slice of the set of current revisionlevel encoded data slices and storage of a previous revision levelencoded data slice of a set of previous revision level encoded dataslices, wherein the data segment with the previous revision level isdispersed storage error encoded to produce the set of previous revisionlevel encoded data slices.
 10. The non-transitory computer readablestorage medium of claim 9 further comprises: the at least one memorysection stores further operational instructions that, when executed bythe one or more processing modules, causes the one or more computingdevices of the DSN to: receive a commit acknowledgement in response to acommit command of the set of commit commands from the one of the storageunits indicating that the one of the storage units has made the currentrevision level encoded data slice available for accessing; issue the setof finalize commands when a predetermined number of commitacknowledgments have been received from the storage units, wherein thepredetermined number is greater than the write threshold number ofcurrent revision level encoded data slices; and not issue the set offinalize commands when a number of received commit acknowledgements isbelow the predetermined number.
 11. The non-transitory computer readablestorage medium of claim 9 further comprises: the at least one memorysection stores further operational instructions that, when executed bythe one or more processing modules, causes the one or more computingdevices of the DSN to: when the determining whether to issue the set offinalize commands is initiated: determine whether a write thresholdnumber of commit acknowledgments have been received from the storageunits; when the write threshold number of commit acknowledgments havebeen received from the storage units, issue the set of finalizecommands; and when the write threshold number of commit acknowledgmentshave not been received from the storage units, issue a set of undocommands to the storage units.
 12. The non-transitory computer readablestorage medium of claim 9 further comprises: the at least one memorysection stores further operational instructions that, when executed bythe one or more processing modules, causes the one or more computingdevices of the DSN to: receive a command to not issue the set offinalize commands.
 13. The non-transitory computer readable storagemedium of claim 9, wherein the finalize command comprises: aninstruction to maintain storage of the current revision level encodeddata slice and to delete the previous revision level encoded data slice.14. The non-transitory computer readable storage medium of claim 9,wherein the finalize command comprises: an instruction to maintainstorage of both of the current revision level encoded data slice and theprevious revision level encoded data slice.
 15. The non-transitorycomputer readable storage medium of claim 9, wherein the finalizecommand comprises: an instruction to delete the current revision levelencoded data slice and to maintain storage of the previous revisionlevel encoded data slice.
 16. The non-transitory computer readablestorage medium of claim 9 further comprises: the at least one memorysection stores further operational instructions that, when executed bythe one or more processing modules, causes the one or more computingdevices of the DSN to: when the write threshold number of writeacknowledgements have not been received within the given period, issue aset of rollback commands to the storage units.
 17. A computing device ofa dispersed storage network (DSN), the computing device comprises: aninterface; a memory; and a processing module operably coupled to theinterface and the memory, wherein the processing module functions to:send, via the interface, a set of write commands to storage units of theDSN regarding storage of a set of current revision level encoded dataslices, wherein a current revision level of a data segment is dispersedstorage error encoded to produce the set of current revision levelencoded data slices; receive, via the interface, a write acknowledgementin response to a write command of the set of write commands from one ofthe storage units indicating that the one of the storage unitssuccessfully stored, but has not made available for accessing, a currentrevision level encoded data slice of the set of current revision levelencoded data slices; determine whether a write threshold number of writeacknowledgements have been received within a given period indicatingthat a write threshold number of current revision level encoded dataslices of the set of current revision level encoded data slices havebeen successfully stored, but are not yet available for accessing; whenthe write threshold number of write acknowledgements have been receivedwithin the given period, issue, via the interface, a set of commitcommands to the storage units regarding making successfully storedcurrent revision level encoded data slices available for accessing; andsubsequent to issuing the set of commit commands, determine whether toissue a set of finalize commands based on one of: receiving a requestfor dispersed storage error encoded storage of a data segment having amore recent revision level than the current revision level and receivinga request to make the determination; wherein a finalize command of theset of finalize commands instructs a storage unit of the storage unitsregarding storage of a corresponding current revision level encoded dataslice of the set of current revision level encoded data slices andstorage of a previous revision level encoded data slice of a set ofprevious revision level encoded data slices, wherein the data segmentwith the previous revision level is dispersed storage error encoded toproduce the set of previous revision level encoded data slices.
 18. Thecomputing device of claim 17, wherein the processing module furtherfunctions to: receive, via the interface, a commit acknowledgement inresponse to a commit command of the set of commit commands from the oneof the storage units indicating that the one of the storage units hasmade the current revision level encoded data slice available foraccessing; issue, via the interface, the set of finalize commands when apredetermined number of commit acknowledgments have been received fromthe storage units, wherein the predetermined number is greater than thewrite threshold number of current revision level encoded data slices;and not issue the set of finalize commands when a number of receivedcommit acknowledgements is below the predetermined number.
 19. Thecomputing device of claim 17, wherein the processing module furtherfunctions to: when the determining whether to issue the set of finalizecommands is initiated: determine whether a write threshold number ofcommit acknowledgments have been received from the storage units; whenthe write threshold number of commit acknowledgments have been receivedfrom the storage units, issue, via the interface, the set of finalizecommands; and when the write threshold number of commit acknowledgmentshave not been received from the storage units, issue, via the interface,a set of undo commands to the storage units.
 20. The computing device ofclaim 17, wherein the processing module further functions to: receive acommand to not issue the set of finalize commands.
 21. The computingdevice of claim 17, wherein the finalize command comprises: aninstruction to maintain storage of the current revision level encodeddata slice and to delete the previous revision level encoded data slice.22. The computing device of claim 17, wherein the finalize commandcomprises: an instruction to maintain storage of both of the currentrevision level encoded data slice and the previous revision levelencoded data slice.
 23. The computing device of claim 17, wherein thefinalize command comprises: an instruction to delete the currentrevision level encoded data slice and to maintain storage of theprevious revision level encoded data slice.
 24. The computing device ofclaim 17, wherein the processing module further functions to: when thewrite threshold number of write acknowledgements have not been receivedwithin the given period, issue, via the interface, a set of rollbackcommands to the storage units.